Digital Matter // PORO(CITY) // Sound Dampening Aggregation

MASTER IN ADVANCED ARCHITECTURE PORO(CITY) DIGITAL MATTER Faculty Areti Markopoulou David Andrés León Fabrication Assistant Raimund Krenmuller Teaching Assistant Nikol Kirova Students Ines Cavar Matin Darabi Hanna Lepperød Ilaena Mariam Napier

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| 2019/2020

sound dampening aggregation

| intelligent constructions

CONTENTS

01 | Abstract .....................

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02 | Context ..................... noise pollution

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03 | Research question ..................... how can we dampen sound?

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04 | State of the art ..................... sound dampening systems and materials

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05 | Sound characteristics ..................... physics of sound 06 | Material system and Exploration ..................... sound dampening properties cork bioceramic moss lichen surface texture binder sound tests

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07 | Design and Fabrication strategy ..................... aggregation as a sound dampening technique stochastic vs deterministic approach

state of the art fabrication 08 | Unit design process ..................... design parameters computational optimization

material layering and fabrication impedance matching

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09 | Case study ..................... 113 site characteristics analysis 10 | Geometry design process computational optimization drawings fabrication process 11 | Conclusion

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12 | References ..................... 161

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01 ABSTRACT

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abstract

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chapter 01

Abstract Car-dependent city planning has resulted in high levels of environmental pollution, sedentary lifestyles, and increased vulnerability to the effects of climate change. Barcelona is a compact city where many uses and activities coincide in one space, which generates different types of sounds and noises. As in most cities, the main sources of noise come from traffic, major transport facilities, leisure activities, shopping areas, and industrial activities.

Noise pollution can be considered as unwanted or disturbing sounds that affects the health and well-being of humans and other organisms. Human ears should not be exposed to more than 85dBA (decibels) for a period of 8 hours a day followed by a 10 hour recovery period at 70dBA or less. If one is exposed to high levels of noise for prolonged periods of time, it can cause a number of negative effects on both health and behaviour, as well as damage psychological health.

Architecture should be designed to reduce the amount of noise we are exposed to and should accommodate spaces where sound becomes an element of comfort. To consider an architecture against noise, we have to first understand the physical principles that govern the propagation of sound and understand how to isolate and arrange a space accordingly.

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The chapters in this paper contain a summary of synthesized reviews of the relationship between material systems and the architectural application of them in order to increase the reduction of noise.

The research aims to showcase a new material system that can be adapted to specific sites and noise sources in order to dampen the effects of noise. This solution was designed and chosen to be cheap and sustainable to combat the growing problem in cities.

An important factor of this project is that the project consists of many complex concepts that interrelate with the main focus on sound and fabrication. In this paper, it was found that sound is a complex principle that is difficult to design for as it cannot physically be seen and there are many different factors that can affect it. Through the use of physical sound tests, computational simulations, and research, this project was able to progress to a feasible solution. With further investigation and material testing, this project will be able to excel.

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02 CONTEXT

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context

Noise pollution As already mentioned, noise pollution is any kind of unwanted or disturbing sound that affects the health and well being of people around it. It is caused by traffic or a large number of people in one place.

More than 360 million people in the world have hearing problems due to exposure to very loud noise. A very big part of this is caused by traffic.

While driving, cars or any kind of vehicles produce noise from 50 to 90 dB which is much more than the dB levels allowed within cities. The Mimi study found that the average city resident has hearing loss equivalent to people 10 to 20 years older. ¹ Research has shown that Barcelona is the seventh loudest city in the world after cities such as Mumbai, Beijing, or Istanbul. The main cause of this is traffic noises, as Barcelona hosts up to 2 million cars.

Often called the perfect city for pedestrians, it is a nightmare for drivers.

Barcelona is composed of blocks with roads on each side. Those roads are often only in one direction which makes the drivers go in circles to come from point A to point B.

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¹Worldwide Hearing Index 2017, Mimi Hearing Technologies GmbH ²Changing the urban design of cities for health: The superblock model Natalie Mueller David Rojas-Rueda Haneen Khreis Marta Cirach David Andrés Joan Ballester Xavier Bartoll Carolyn Daher Anna Deluca Cynthia Echave Carles Milà Sandra Márquez Joan Palou

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chapter 02

To solve the problem of noise pollution caused by traffic, Salvador Rueda came up with the idea of the ‘Superblock’. Superblocks are clusters of nine blocks, where traffic is restricted to major roads around the outside, opening up entire groups of streets to pedestrians and cyclists. These streets are filled with benches and playgrounds for people to congregate.

This approach is very interesting, and besides the environmental benefits such as reducing noise and air pollution, it creates new public spaces for people to interact.

Barcelona is also well known for its nightlife. Even on regular days, many bars work until 2 or 3 am which makes it impossible for the residents not to be disturbed during the night hours. During the daytime, especially in the old town areas, such as el Born, there is a large amount of tourists walking by that create noise. digital matter | intelligent constructions

To conclude, noise pollution is all around us, it affects our health, physical and mental. According to IS Global, it can be associated with discomfort and stress, poor performance, sleep disturbance, and even heart diseases, hypertension or diabetes and obesity. Noise pollution is a very serious thing but unfortunately, it is still not taken that seriously. Research has shown that it creates at least as many diseases as air pollution. ³ Noise is a growing problem in our cities and in order for a better and healthier future, it needs to be more taken care of.

³publication from the Communications and the Urban Planning, Health and Environment Initiative at ISGlobal. Authors and collaborators (in alphabetical order): Ione Avila-Palencia, Xavier Basagaña, Aleix Cabrera, Glòria Carrasco, Ariadna Curto, Payam Dadvand, Carolyn Daher, Irene Eleta, Beatriz Fiestas, Maria Foraster, Mireia Gascon, Haneen Khreis, Èrica Martinez, Mark Nieuwenhuijsen, Natalie Mueller, David Rojas, Pau Rubio, Adelaida Sarukhan, Marta Solano, Jordi Sunyer, Raül Toran, Margarita Triguero and Wilma Zijlema. LAST UPDATE: APRIL 2018

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03 RESEARCH QUESTION

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research question

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chapter 03

How can we dampen the sound?

Over the centuries, architectural tastes have changed, leading to a visualchange in interior design, which has resulted in a physical change in the acoustics of rooms. In grand palaces and concert halls built before the twentieth century, statuary, relief work and other ornamentation used to be commonplace, providing ample surface scattering, and presumably a more diffuse sound field. This style was replaced in the twentieth century by a simpler look. Many auditoria and rooms from the twentieth century contain large flat surfaces, which in turn leads to more specular and less diffuse reflections. There is also a suggestion, that with the greater precision of twentieth century engineering, and consequently these flat areas became more precise than the more hand-crafted older building, leading to more exacting specular reflections.¹ We can learn from theory that there is a complexity that is appealing to us, no matter the context. Urban sounds can be enjoyable for people in need of high complexity information. At the same time urban planners need to respect those who do not find the high complexity of sounds as attractive.

If a sound is very complex, it is often “unreadable” and people tend to become annoyed by the unwanted sound (i.e. a jet engine, a sewing machine).

If the sound complexity is too low, the sound is not interesting or attractive to the person. There is an intermediate level of complexity, a sweet spot between these two extremes, which generates the best possible feelings from the widest variety of individuals. For example, the human voice is a complex sound, but it has the right amount of complexity that we find it enjoyable.²

There are fundamental interactions that take place when a sound impinges upon a material: some energy is reflected back, some energy is absorbed into the material(converted into a small amount of heat), and some energy may be transmitted through the material to the other side. All materials absorb, reflect, and transmit sound in their own particular way which will be discussed in the Material Systems chapter in detail.

Nevertheless, generally just as the material composition of an environment establishes visual identity, it is may also form an aural identity.³ Our goal is to create urban infrustructures zones with different acoustical complexity. Complete silence in an Urban space is impossible but we can make the noises dimmed or masked. There are many ways for dampening the sound such as vegetation, water or acoustic panels. Since product has an urban scale should be desirable for the citizens as well.

As you walk around the city you can notice how sound is effected by plants and physical barriers. To understand how these objects work, we have to understand what is sound.

What does this mean for designers, planners, and engineers working in this environment?

¹ ACOUSTIC DIFFUSERS: THE GOOD, THE BAD AND THE, T J Cox, Salford University ²What is soundscape ecology? An introduction and overview of an emerging new science, Bryan C. Pijanowski • Almo ³Sound Materials – A Compendium of Sound Absorbing Materials for Architecture and Design

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chapter 03

Sound absorbing materials are typically said to manipulate the environment, either to quiet a source of noise or to enhance the reception of sound. In many areas, while using specific materials, in the scale of surface, the complexity of texture may cause the sound to reflect more diffusley, while a flat, monolithic surface will refelct speculary. This interaction is also dependent upon the sound’s wavelength in relation to the dimension of the surface patterning.

Acoustics is an extensive field of study and it has many complex layers that contain a variety of disciplines such as mechanical, psychology, medicine, music, engineering, architecture, art, and speech communication.

In the primary stages, the acoustic environment can be broken down into three elements: the source, the path, and the receiver. The source is whatever that is producing sound. The path is the medium through which the sound transmits, which can be the air or something physical like a material.

The receiver might be a listener or even a microphone.

In physical terms, a sound is a mechanical wave that propagates through a medium which can be a solid, gas or liquid. This all will be results in microscopic changes in the local pressure.

Porous absorbers are the most common type of acoustically absorptive material - soft, fuzzy, spongy materials like fiberglass, foam, and heavy textiles. With porous materials, sound absorption occurs due to interconnected pores creating viscous effects that cause acoustic energy to be dissipaed as heat. In order for this to occur, the pores must be interconnected throughout the material and these pores must be open or exposed to the environment.

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There are three categories according to their porous micro-structures: namely cellular, fibrous, and granular. The absorptivity of porous materials is primarily related to porosity and flow resistivity. Porosity can be defined in terms of the fractional amount of air volume within the material. The higher the porosity, generally, the better the absorptivity. Glass and stone wools can have a porosity of around 98 percent.

The properties that need to be considered when it comes to porosity is that they must be open and interconnected so that they are entirely isolated from their neighbors are called “closed” pores or cells. They have an effect on some macroscopic properties of the material such as its bulk density, mechanical strength, and thermal conductivity but lost pores yield significant sound absorption. Closed cells do not count toward a material’s total porosity.

Porous materials can also be categorized in terms of their flow resistance a measure of the resistance experienced by air when it passes through the open pores in the material. If the flow resistivity is too high, then there is an impedance mismatch between the air and the materials causing the sound to reflect rather than absorb into the material.

Going on to fibrous materials, an important parameter is the diameter of the fiber as this relates to flow resistance. There two kinds for this aspect, first are the synthetics and second id the natural fibers. Natural fibers tend to have a slightly larger diameter than some of the synthetic fibers that are commonly produced.

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04 STATE OF THE ART

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state of the art

Sound dampening systems and materials In order to develop a project for dampening the sound, it is very important to fully understand what was has previously been used and how these technologies and phenomenons work.

State of the art is the catalogue gathering all the important sound dampening technologies, phenomenons and techniques that can help to deeply understand the ways of sound reduction.

This was the starting point of the project and very first contact to sound physics for all the participants.

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chapter 04

1// Anechoic chamber is a room designed to absorb sound or electromagnetic waves. By “anechoic” it means “echo-free”.

The whole space is lined up with fiberglass wedges that help to dampen any kind of sound. They cover the entire ceiling, floor and walls. Wedges are designed to make the sound waves reflect from one wedge to another and in that way lose almost all of its energy. In 2015, Microsoft’s anechoic chamber measured a background noise level of -20.3dB(A). This was verified as a new world record by Guinness World Records. *Guinness World Records article:Microsoft lab sets new record for the world’s quietest place written by

By Rachel Swatman Article: Inside the world’s quietest room written by Jacopo Prisco Image source: Antenna Test Lab Co’s Anechoic Chamber

2 // Schroeder diffuser, invented by Manfred R. Schroeder in 1970s is a structure comprising a number of wells of different, carefully chosen depths. As a soundwave strikes the irregular surface, instead of bouncing off it like a mirror, it bounces out of each well at a slightly different time. The result is many small reflections, spread out in both time and space. *Visualization of the sound field around a Schroeder diffuser K.Fujiwara K. Nakai H.Torihara Image source: Acoustic Diffuser Schroeder 4, Pikacoustics

3 // The Elbphilharmonie is a concert hall project in the northern German port town of Hamburg made by Herzog & de Meuron.

The heart of the project is the Great Hall, developed in collaboration with the highly esteemed acoustician Yasuhisa Toyota. It seats 2,150 people and exhibits a highly advanced, custom developed acoustic interior skin. The curvilinear, intricately intertwining wall, balustrade, and ceiling design of the Great Hall are comprised of 10,000 unique gypsum fiber panels with a special sound diffusing pattern applied to each piece, which all fit together like a large puzzle. *Digital Fabrication Of Non-Standard Sound-Diffusing Panels Inthe Large Hall Of The Elbphilharmonie Author(S): Benjamin S. Koren And Tobias Müller and Book Title: Fabricate 2017 Image source: courtesy of Johannes Arlt

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state of the art

4 // During NASA’s launch pad water deluge at Kennedy Space Center, there are six 12-foot high nozzles, called rainbirds. At main engine ignition, a torrent of water flows onto the mobile launcher. Nine seconds after liftoff, 900,000 gallons of water per minute are spraying through the area to reduce the acoustical levels in the payload bay area to about 180 decibels (dB). As a frame of reference, a quiet home emits about 40 decibels of noise, amplified rock and roll music is about 120 db at 100 feet, and a jet plane gives off 130 db at 100 feet. *Excerpted from NASAexplores

5 // Helmholtz resonator is a container of gas with an open hole.

A volume of air in and near the open hole vibrates because of the ‘springiness’ of the air inside. A common example is an empty bottle: the air inside vibrates when you blow across the top.

The name came from the inventor Hermann von Helmholtz who used it in the 1850s to to identify the various frequencies or musical pitches present in music and other complex sounds. * The University New South Wales, article called Helmoltz resonance by PhD student and luthier John McLennan

6 // Destructive interference is a phenomenon that occurs when the crest of one wave and the trough of another wave intersect.

The amplitude of each wave substract to form a wave with a smaller amplitude. For example noise canceling headphones are working by using destructive interference. A microphone picks the frequencies of incoming waves. The headphone then sends out a wave that is the exact opposite, canceling out the sound.

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7 // Acoustic black holes are relatively new physical objects that have been introduced and investigated mainly during the last decade. They can absorb almost 100% of the incident wave energy. The main principle of the acoustic black holes is based on a linear or higher order decrease in velocity of the incident flexural wave with propagation distance to almost zero. The decrease in velocity should be accompanied by efficient energy absorption in the area of very low velocity via insertion of small pieces of absorbing materials. * Acoustic black holes for flexural waves: A smart approach to vibration damping, Victor V. Krylov 8 // Noise barriers are one of the most popular ways of reducing unpleasant sound in the cities. Noise barriers work by blocking the direct travel of sound waves from a source (such as a highway) to adjacent homes or businesses, forcing the waves over the top or around the barrier. The barrier must be high enough and long enough to block the view (line of sight) of the highway.

Barriers are most effective for the first one or two rows of homes at distances up to 60 meters from the barrier. As noise levels decrease with distance, there is a point away from the highway at which noise barriers are no longer effective. * Location of noise barrier and their effect on road safety, Author: Slavcheva Semedzhieva

9 // Vegetation is not only good for helping clean the air but it also helps us to reduce the noise. One way is absorbing the sound. The absorption is happening through plant parts such as stems, leaves, branches, wood etc.When sound hits a masonry wall, the wall does not vibrate (because it is rigid). Sound waves are reflected off the wall and back toward the source. But when sound waves hit a flexible material such as plants, the material vibrates and the waves are transformed into other forms of energy. digital matter | intelligent constructions

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05 SOUND CHARACTERISTICS

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sound characteristics

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chapter 05

Physics of sound A sound wave is a longitudinal mechanical wave that is caused by the vibrating object. Sound is produced by a vibrating object that causes the surrounding medium (solid, liquid or gas) to vibrate. When waves are moving through the medium, the particles vibrate back and forth.¹ What characterizes sound waves as longitudinal is that the motion of the particles is parallel (and anti-parallel) to the direction of the energy movement.

Sound waves consist of areas of high pressure called compression and the areas of low pressure called rarefactions. One wavelength is the distance over which the wave’s shape repeats.

There are two main properties of a sound wave: 1. The amplitude 2. The frequency The amplitude is the size of the vibration. It is the height of the wave. It determines how loud the sound will be and it is measured in decibels (dB).

Frequency is the speed or duration of the vibration. It is measured as the number of wave cycles that occur in one second. The unit of frequency measurement is called Hertz. For example, 1 Hertz, means that there is only 1 wave cycle per second. Frequency determines the pitch of the sound.

A longer wavelength means a lower pitch whereas a shorter wavelength means a higher pitch.

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¹ Sound Materials – A Compendium of Sound Absorbing Materials for Architecture and Design, Tyler Adams

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One of the most relevant references for the sound dampeningwould be highway noise barriers. Almost all the noise barriers you will see have concave shape. Why? To begin with, the sound travels from the roads going through barriers and reflects off of them. In this way, by creating concave shape all the noise eventually comes to one point. In the normal environment, this would be a huge problem as the noise would be enormous. But if the situation was inverted, and the barriers were convex all the noise would scatter around.

Even though it would be slightly lower, it would still affect the environment around much more than it is right now.

This is the main issue with flat noise barriers. If they are not high enough, the sound reflects around and goes above the barriers in the neighbourhoods. According to the research, the barriers might be beneficial for the first 15 to 60 meters but all above that brings more noise to the neighbourhoods than not having the barriers.The sound is not being dampened but amplified.

Taking this into consideration, we concluded, that by applying the porous structure with a lot of gaps and uneven surfaces, the sound would reflect much more within the structure itself and in that way lose its energy.

ยนOn Highway Noise Barriers, the Science Is Mixed. Are There Alternatives? BY MERYL DAVIDS LANDAU, 2017

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We looked at how sound is measured by these two spectrums. The decibel and frequency range. Frequency is the number of vibrations or cycles of sound per second measured in hertz and determines the pitch of the sound. Decibels measures the strength of these vibrations and can determine the loudness of sound.

The common range of human hearing is between 20 and 20 000 Hz. However, there are some variations between the individuals, especially at high frequencies.There is a gradual loss of sensitivity to higher frequencies with the coming of age. Several animal species are able to hear frequencies much higher than humans. As an example, dolphins and bats can hear frequencies up to 100,000Hz. On the other hand some whales can hear sounds as low as 7Hz. Looking at the most annoying noise sources, we figured out that the biggest issues in our society considering the noise pollution right now are traffic noise and human voice (in public spaces).

Our main focus is to tackle the range of frequencies coming from these frequencies. These frequencies range between 200 to 1300Hz (traffic noise range from 700 to 1300Hz whereas the human voice ranges around 200 based on the individuals).

Considering the loudness of the noise that is measured in the decibels, our goal was to reduce the sound levels for the environment not to be harmful.

Between 0 and 80dB(A), the sound is not harmful to people except if they are in the presence of the sound for a long period of time. Everything above 90dB(A) is very harmful and can endanger one’s health. Just as a reference, the decibel range of a rock concert is 110dB(A) or higher.

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06 MATERIAL SYSTEM and EXPLORATION

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material system and exploration

Sound dampening properties Sound-absorbing materials absorb most of the sound energy striking them, making them very useful for the control of noise. They are used in a variety of locations – close to sources of noise, in various paths, and sometimes close to receivers. Although all materials absorb some incident sound, the term “acoustical material” has been primarily applied to those materials that have been produced for the specific purpose of providing high values of absorption. The major uses of absorbing materials are almost invariably found to include the reduction of reverberant sound pressure levels and, consequently, the reduction of the reverberation time in enclosures, or rooms. A wide range of sound-absorbing materials exist. In the 1970s, public health concerns helped change the main constituents of soundabsorbing materials from asbestos-based materials to new synthetic fibers.

Although, these new fibers are much safer for human health, more recently, issues related to global warming may increase the use of natural fibers instead of synthetic ones. ¹

Porous sound-absorbing materials have evolved into more advanced materials over the years. Compared with the older absorbing materials produced in the 1960s, the new materials have become safer, lighter and more technologically optimized. In addition, the concept of environmentally friendly, sustainable, recycled, and green building materials will soon have an important role in the marketing of sound-absorbing materials. These new directions will hopefully encourage the development of new materials and/or the improvement of existing ones. Given the intensity of research and the development in manufacturing processes, we anticipate that the range of new sound-absorbing materials will expand quickly over the next few years.

When sound collides with a surface, it interacts with and responds to the material and formal conditions of that surface. These interactions, are conveyed to the listeners when sound reflects from the boundaries of our environment and arrives at our ears. Every material reflects or absorbs sound in their own particular manner.

Materials designed specifically to absorb sound may be found in a wide variety of everyday environments - classrooms, subway stations, lobbies, airports, auditoriums, offices, factories, museums, and swimming pools.

Sound-absorbing materials are used to reduce noise, to improve speech communication, to enhance the listening experience of music and for control reverberation. Often the acoustic design and engineering of those environments goes unnoticed.² ¹ A Compendium of Sound Absorbing Materials for Architecture and Design ² Recent Trends in Porous Sound-Absorbing Materials Jorge P. Arenas, University Austral of Chile, Valdivia, Chile Malcolm J. Crocker, Auburn University, Auburn, Alabama

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chapter 06

The three main type of porous Cellular

Fibrous

Granular

Porous absorbing materials can be classified as cellular, fibrous, or granular; this is based on their microscopic configurations. Porous materials are characterized by the fact that their surfaces allow sound waves to enter the materials through a multitude of small holes or openings. Materials made from open-celled polyurethane and foams are examples of cellular materials. Fibrous materials consist of a series of tunnel-like openings that are formed by interstices in material fibers. Fibrous materials include those made from natural or synthetic fibers such as glass and mineral fibers.¹ In addition, a porous absorbing material can also be granular. Consolidated granular materials consist of relatively rigid, macroscopic bodies whose dimensions exceed those of the internal voids by many orders of magnitude (agglomerates). Unconsolidated materials consist of loosely packed assemblages of individual particles(aggregates).²

¹ Kazragis, A., Gailius, A., and Jukneviciute, A., “Thermal and Acoustical Insulating Materials Containing Mineral and Polymeric Binders with Celluloses Fillers,” Material Sciences, Vol. 8, No. 2, pp. 193-195, 2002. ² Recent Trends in Porous Sound-Absorbing Materials

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// Aerogels are another form of microporous materials used in some complicated applications. Aerogels are also known as frozen smoke and have been claimed to be the best thermal insulators ever made, being 40 times better than common fiberglass insulation materials.Aerogels are created by removing the liquid content of a gel by a supercritical drying manufacturing process. An aerogel has a monolithic interna structure being made of a highly porous, extremely lightweight and translucent material in which most of its volume is filled with air. Several raw materials have been used to produce aerogels, but silica aerogels are the most common.

Its structure is composed of small spherical silicon dioxide clusters from 3-4 nm in diameter that are linked to each other forming chains that in turn form a spatial grid with air-filled pores.The typical average size of the pores is 30 to 40 nm. The typical porosity of an aerogel is greater that 75%, and its melting point is 1,200° C.¹ Although the production of metal foams, ceramic foams, and aerogels can contribute to greenhouse gas emissions, their practical use in transporttion will help in reducing other emissions.² // Nanocellulose is a renewable and biocompatible nanomaterial with a high-strength low-density and tunable surface chemistry. Cellulose is a homopolysaccharide consisting of a linear chain of linked anhydroglucose units (AGU). The combination of an ultralow density,tunable,porous, architectureand outstanding mechanical properties makes them of interestfor a wide range of applications including e.g. biomedical scaffolds, thermal insulation and devices for storage and generation of energy.³ Due to a lack of manufacturing processes, cellulose fibers are rarely used as raw material for obtaining porous or low-density materials in insulating applications. Yet recent research has highlighted an innovative way to produce highly porous materials based on cellulose fibers. This method includes a foam-forming process where cellulose fibers and other components are mixed with a foaming agent instead of water, as is common in conventional methods.

The result is a lightweight material with low-density that is mechanically pressed with a load that increases strength.

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Foam-formed cellulose materials (FCM) were obtained by mixing a surfactant with cellulose fibers and then tested with promising results on sound absorption applications.5 The cellulose loose-fill composite materials obtained by the aforementioned foam-forming methods represent an alternative solution for soundproof, especially compared with applications obtained using conventional methods. Furthermore, this method can be applied on both virgin and recycled cellulose fibers.6 // Natural moss Natural moss can be processed and preserved so it can create a decorative and acoustically absorptive finish that is long-lasting, maintenance-free, and it does not need any artificial light, fertilizer, or water.

A 50mm thick moss pre-mounted to 10mm thick MDF, panelized or even suspended like a pendant, is an effective absorber at high frequencies above 500Hz.

¹ Schmid, M., and Schwertfeger, F., “Applications for Silica Aerogel Products,” Journal of Non-Crystalline Solids ² FKA, Determination of Weight Elasticity of Fuel Economy for Conventional ICE Vehicles, Hybrid Vehicles and Fuel Cell Vehicles, Report 55510, Forschungsgesellschaft Kraftfahrwesen mbH, Aachen, 2007. ³ Nanocellulose-based foams and aerogels:processing, properties, and applications,Nathalie Lavoine and LennartBergstrom 4 Li, R.; Du, J.; Zheng, Y.; When, Y.; Zhang, X.; Yang,W.; Lue, A.; Zhang, L. Ultra-lightweight cellulose foam material: Preparation and properties. Cellulose 2017, 5 Nechita, P.; Nastac, S. Foam-formed cellulose composite materials with potential applications in sound insulation. J. Compos. Mater. 2018.

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Cork // Cork is a very lightweight material, elastic and flexible and impermeable to gases or liquids, imperishable and good electric insulator, as well as thermal, sound and vibration insulator and a dielectric material. As a cellular material its unique properties arise from its closed cell structure.¹ In the market there are several types of cork agglomerates. Cork agglomerates are divided into two categories: composition cork and insulation corkboard.

The second category is made of only cork without any external binding agents or any other added material and so it cannot be considered as a true composite material and will therefore not be discussed in this review.

Composition cork is made by the binding of cork particles with different binders (polyurethane, melamine, rubber etc) yielding products such as agglomerated cork stoppers, floor coverings, joints, etc. The physical and chemical characteristics of the binders determine the strength of agglomerate and therefore its application.² Cork is a pretty extraordinary material and that is why it has so many uses.

The key to cork’s many properties is its honeycomb cell structure. Each cell is a 14-sided polyhedron filled with air with an extremely strong and flexible membrane that is waterproof and airtight. Cork bark is in fact about 89% air, giving it a very low density, but when it is compressed the air is not squeezed out, because the cell membranes will not release it, which is why it will return to its original shape when the compression is removed. absorb water and gain density/mass in humid conditions. That is why for example it is the perfect product to use for fishing floats.

Cork was one of the first materials that Robert Hooke (1635-1703)observed on the optical microscope. After this observation Hooke defined a base unit for the structure of plants and biological tissues, which he referred to as “cell”. The microstructure of cellular materials is based on hollow voids (the cells) separated by material walls. In the case of cork cells are closed and its volume fraction accounts for 85%. Cells walls are a composite formed by natural polymers: suberin, lignin and cellulose. digital matter | intelligent constructions

During cell growing, cell wall membrane thickens. This thickening is derived from the deposition of layers with different structures and chemical compositions. Generally it is considered that the cell wall is composed by primary, secondary, and tertiary walls with different chemical compositions. In 1877, Von Hohnel proposed one of the first models to the structure of cork cell wall. According to this model, the wall that separates two cells is made up of five layers. Cork is therefore a vegetable material with exceptional environmental qualities. It is a renewable, recyclable, non-toxic and durable natural resource with excellent physical and mechanical properties.

Microscopically, cork’s internal microstructure is made up of layers of alveolate cells, whose membranes have a high degree of impermeability.³

¹ Gil, L.; Silva, P. Cork Composites. In ECCM9-Composites: From Fundamentals to Exploitation,Brighton, UK, June 4-7, 2000. ² Gil, L.; Moiteiro, C. Cork. In Ullmann’s Encyclopedia of Chemical Technology, 6th ed.; Wiley-VCH: Verlag, Germany, 2003. ³ its origin in the papers of the2nd International Conference of Biodigital Architecture & Genetics, curated by Alberto T.

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Nothing is wasted and everything is valued. From natural to highest demanding applications, the cork waste is recycled in all stages of the valuechain.The cork dust is used in electrical cogeneration, improving energy efficiency and Over 60% of the companys energy needs are met by using biomass (cork dust) which is a CO2 neutral source of energy.

The first agglomerated cork stoppers were developed in the beginning of the XX century using several types of glues (dextrin, casein, gelatin, urea-formaldehyde, amine) and in 1968 polyurethane.¹ Several undoc mented experiments were carried out at an industrial level and lead to many of the current commercial cork composites.

There are several types of cork agglomerates. Cork agglomerates are divided into two categories: composition cork and insulation corkboard.

The second category is made of only cork without any external binding agents or any other added material and so it cannot be considered as a true composite material and will therefore not be discussed in this review. Composition cork is made by the binding of cork particles with different binders (polyurethane, melamine, rubber etc) yielding products such as agglomerated cork stoppers, floor coverings, joints, etc. The physical and chemical characteristics of the binders determine the strength of agglomerate and therefore its applications.² The production of cork rubber is similar to other rubber-like product production. Rubber and cork granules are mixed in rolls and the mats obtained are introduced into a mould, which is heated for polymerization. Usually blocks are obtained, but cylinders can also be obtained. The blocks are sliced and the cylinders are cut (unrolled) to produce rolls. The heating process may take from several hours (in a typical oven) to some minutes (in microwave systems). Most common cork rubber materials use cork granulates of 60-70 kg/m3, in 15 to 260% by weight in relation to rubber.¹

The granules with a specific granulometry and volumetric mass are placed into a mixing device (shovel or helicoidal mixers) for automatic or manual dosage. A mixture of cork granules and glue and/or other additives are put into a mould (usually metallic and paralelipipedic in shape or cylindrical for rolls) which is then closed and heated, usually at more than 120 oC and in tunnels, for 4-22 hours, in order to produce a block which upon cooling (or not) is then sliced into sheets, which are then dimensionally finished. By using various binding agents and chemical additives it is possible to adapt the grade to suit user requirements and the purpose for which the material is to be used. These products are usually produced in sheets, rolls, blocks, or tiles, with different thickness, densities and finishing: simply polished, waxed, painted, varnished or covered with a vinyl layer or even extruded or moulded. The group with a vinyl layer may use a decorative sheet between the PVC (polyvinyl chloride) and the agglomerate underneath.² A composite corkplate is described in a European patent. This material comprises a carrier layer of compacted glues lignocellulosic particles, namely wood chips or fibers and, at least, one covering layer made of glued cork particles. The covering layer is bound to the carrier by simultaneous and mutual compression. This patent also includes a multilayer material which has, at least, one of the exterior surfaces of the plate made of glued cork particles and the middle layer is made of glued lignocellulosic particles. The plate has a density of 0.4-0.8 g/cm3.³ Cork makes good gaskets because it accommodates large elastic distortion and volume change and its closed cells are impervious to water and oils. The recovery capabilities of cork after compression are also important for gaskets, allowing a continuous pressure against both sealed surfaces. In footwear applications, cork materials are ideal to the technical demands of the shoe industry and can be used in insocks/insoles, heels, sole and bottom fillers, mid soles, coverings,footbeds (moulded applications). ¹ Gil, L. História da Cortiça; APCOR: Santa Maria de Lamas, Portugal, 2000. ² Gil, L.; Moiteiro, C. Cork. In Ullmann’s Encyclopedia of Chemical Technology, 6th ed.; Wiley-VCH: Verlag, Germany, 2003.

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The cell structure of cork gives it the following properties: - Elastic and Resilient: The flexibility of the cork cell membranes are extremely flexible, compressible and elastic, so it will always tend to return to its original shape, no matter what sort of pressure it is put under. This makes it a fantastic product to use for bottle stoppers, because even after years of compression in the neck of a bottle, it still retains its elasticity so maintaining an airtight seal. You will see this when you remove a cork from a bottle that it will instantly swell back to its original size, making it difficult to fit back into the bottle, no matter how old the bottle is.

- Light: Cork’s low density means that it floats on water; moreover the fact that it has such strong watertight cell membranes means that it will not absorb water and gain density or mass in humid conditions. That is why for example, it is the perfect product to use for fishing floats.

- Insulation: Cork gives a very low conductivity of heat, sound and vibration, mainly because the cell honeycomb structure means that it is made up of lots of tiny, sealed pockets of air which give it incredible insulation properties that are also very durable. In its natural form, cork is also a very good fire retardant, although cork dust is actually extremely flammable (because here the cell structure has been broken down).

- Impermeable: Cork has a chemical in its cell membrane that makes it completely impermeable to liquids and gases. This chemical is a mixture of fatty acids and heavy organic alcohol called suberin, which as well as rendering cork impermeable also stops it from rotting or degrading over time.

- Durable: Cork is extremely durable and has a high friction coefficient, so will survive repeated impact or rubbing extremely well. This means that it can be used for example in cork shoe soles or for industrial applications that require high levels of resistance.

- Hypoallergenic: Cork does not absorb dust, so is ideal for use by people who suffer from allergies or asthma. The fact that cork flooring and cork wall coverings are very easy to clean, also add to its hypoallergenic properties.

digital matter | intelligent constructions

Cork manufacturing process: -Die Cutting: Available for rolls and sheets Max thickness 7mm Max area of 1200mm x 700mm Not suitable for high-density materials Low-cost tools -Lamination:

Available in sheets and rolls

Customizable layer thickness

High efficiency process

Easy gluing (wood, textiles and foams)

Possible to combine cork with rigid and flexible surfaces

Possible to associate multi-materials

Wide range of cork visuals and densities

High resistance & low-weight

Good for acoustic/thermal applications with natural cork visual -Machining: Milling / Cylindrical / Cutter /Turning

Suitable for high density materials

Low cost tools

Small grain size

Suitable for sample/prototype production -CNC Milling:

Allows more complex shapes than milling

Best surface finishing with small size granules

Suitable for high/mid density materials

High-tech process

5-axis machining -Compression Moulding:

Max area of 450mmx900mm

Complex geometries possible with no waste

Faster production cycles than machining

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Bioceramics One of the first materials we looked into, based on its high porosity ratio, was Bioceramics. After some research and experimenting, we found that the process of making bioceramics is expensive and laboursome. The results were limiting in size, which would ultimately affect the scaling-up of the material.

Bioceramic material is currently being used in medicine. Calcium phosphate based biomaterials have been used as bone graft with great success in the last decade. This material is employed in orthopedic and dental applications depending on their specific properties. Ceramic has chemical compositions closely resembling that of the mineral phase of natural bone. Many in-vivo experiments have confirmed the HAP(Hydroxyapatite) as a potential implant material for biomedical applications.¹ To fabricate bioceramics with a porous configuration, the evidence of tissues ingrowth and biological responses provide obvious advantages in tissue-implant fixation and controlled biodegradation rate for both short-term and long-term implantation purposes. Hydroxyapatite ([Ca10(PO4)6(OH)2], HA or HAP), one of the most representational is one of the most representational,which exhibits the outstanding biocompatibility and bioactivity with bone replacement in living tissues, has raised considerable attention in these materials as excellent candidates for orthopaedic, dental andmaxillofacial applications.² Porous HA has been applied for cell loading,drug releasing agents, chromatography analysis,and most extensively for hard tissue scaffolds. One important aspect in preparing the ceramics by means of the slip casting route is microstructural uniformity. For the fabrication of the porous HAP ceramic, the uniformity of macropore distribution is the major consideration. Therefore, it is critically important to retain a reasonable slurry rheology to facilitate the casting operation and/or to stabilise the PVB particles uniformly dispersed in the slurry.³ digital matter | intelligent constructions

How to make high porocity bioceramic?

Based on previous research of Hydroxyapatite bioceramic with large porosity, in 2017, a new mixture of materials and methods had been used.

The materials used were gelatin powder (Weishardt International, Graulhet, France), hydroxyapatite powder (Prayon, Belgium), and polymethacrylicacid as an anionic polymeric dispersant (Sigma Aldrich Chemical, France).

The ceramic preparation process involves three main steps: 1. preparation hydroxylapatite suspension, 2. drying and 3. sintering. Three different mixtures of HA-gelatin were prepared by mixing 5, 10 and 20% of gelatin (percentages with respect to solid HA) with appropriate amounts of hydroxyapatite, and corresponding distilled water contents. The obtained paste was cast and placed in molds that can be opened (10 × 10 × 2.5 cm or 20 × 20 × 2.5 cm).

Results show that the increase of gelatin amounts during the preparation of green bodies increase the percentage of porosity after sintering. For example from 5% to 20% gelatin although the porosity pass from 50.3% to 70.5% respectively at T = 1000 °C. Note that when the temperature increases from 900 °C to 1200 °C, the porosity decreases from 62.1% to 43.58% for 5% of gelatin and 73.5% to 68.5% for 20% of gelatin. The two parameters, gelatin’s percentage and temperature, affect the porosity so that the increasing amount of gelatin is due to the increasing porosity. On the other hand, the density of the ceramic is greater at T = 1200 °C than at T = 900 °C. The pore size in our HA bioceramics are distributed in the range of de 5 μm.

From the SEM images, we see that the pores are interconnected.

Large pores exist in the bioceramics, this phenomenon occurs because the gelatin particles have an important size in order to produce a large pore (size of the gelatin swollen in water).⁴ ¹ Preparation and Characterisation of a Porous Hydroxyapatite Bioceramic via a Slip-Casting Route, Dean-MO Liu,1997 ² Characteristics, preparation and improvement of porous hydroxyapatite bioceramic materials, Volume 8 Issue 11 ³ Materials Science & Engineering C, Hydroxyapatite bioceramic with large porosity, M. Mbarki, P. Sharrock, M. Fiallo, H.ElFeki ⁴ Hydroxyapatite bioceramic with large porosity. M. Mbarki a,P. Sharrock b, M. Fiallo b, H. ElFeki a, 2017

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Calcium phosphates (CaP) based materials, specifically hydroxyapatite and tricalcium phosphate (TCP), are extensively used as synthetic bone graft substitutes for various applications (e.g. bone augmentation procedure) or as biomaterials for in vitro evaluation (e.g., in vitro bone tissue models).

Until now, these bioceramics have been mainly produced with traditional ceramic processes (e.g. porogen leaching, phase separation, gas foaming, replication of PMMA template, bone machining). These conventional methods suffer from architectural limitations, internal inhomogeneity and sample-to-sample variations. This lack of architectural standardization prevents the rigorous design of biological experiments, their reproducibility, etc., which may lead to misinterpretations.

After mixing the materials based on the recipe, we tried to increase the time for baking them (drying) samples in a microwave. As we increased the time the porosity of the material as well as the viscosity, rose.

Due to lack of equipment, cost, and time we decided to look at other porous materials.

New engineering developments combining computational methods and additive manufacturing (AM) technologies are able to overcome such limitations by providing a higher level of control over the design of manufactured scaffolds with the opportunity to create optimized custom architectures in a reproducible way.

However, the “direct” AM technologies, such as ceramic ink writing, stereolithography, or selective laser sintering and melting, still have major drawbacks such as their lack of accuracy and flexibility from one bioceramic phase composition to another, the changes in the chemical and phase compositions (especially for CaP), the post-processing issues (e.g. the removal of raw materials), and their cost. A reliable alternative may be found in the ‘’indirect’’ AM methods, where the outstanding potential of ‘’direct’’ AM technologies for polymers is combined to traditional ceramic impregnation processes. Although the “indirect” AM method is not new, it is still relevant compare to “direct” methods provided that some technical challenges are dealt with properly.

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Moss It is well known that vegetation is very good for sound absorption, which is why you won’t find many busy urban roads without trees nearby. Plants are very appealing to the eye and create a peaceful environment. As well as trees, there are numerous plant types that are very good at sound absorption such as moss, bushes, shrubs.

Moss is a small, flowerless plant. It is divided into two general types, Pleurocarpous and Acrocarpous. Pleurocarpous is known for growing low on the ground and spreading out horizontally whereas acrocarpous grows primarily in clumps and grows vertically.

As a result of being a non-vascular plant and having no roots, moss uses rhizoids to attach to the ground. The main problem of rhizoids is that they dry out quickly so moss needs to be in a moist environment at all times, which is why it is more commonly found in damp, shady locations. There are very few species that can withstand being in the perminently sunny areas.

It’s popularity comes mostly from the ability to clean the air from pollutants, but is also popularly used in sound absorbing panels because of its sponge-like texture. There are numerous projects using moss for noise dampening purposes.

As already mentioned, moss has a very soft, sponge-like surface which results in sound waves getting absorbed instead of reflected.

Moss can be placed on the noise reduction coefficient scale, which ranges from 0 to 1 (where 1 is perfectly absorptive and 0 is perfectly reflective) Moss is located at 0.96, meaning that it is an extremely absorptive material.

Even though it requires very low maintenance, moss can be very demanding. It thrives in a damp, shady environment, it needs a lot of moisture, and it craves acidic soil (from 5 to 6 pH). If the soil or any kind of surface inwhich moss is growing on is not acidic, fertilizers such as yogurt or calcium carbonate can be added to increase the pH levels.

Moss is an amazing material, but due to the case study and location of the project being Barcelona where daily temperatures are hot and moisture is not as present, moss would not thrive. We chose another plant that is more suited to the environment. However, on a global approach, moss would be included if the conditions would allow for it.

We decided to look into Lichen as an alternative.

Moss is most efficient at absorbing higher frequencies between 1000Hz and 2500Hz. This means it absorbs traffic noises which range from 700Hz to 1300Hz which are the most disturbing frequencies to the population.

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Noise Reduction Coefficient

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pros

MOSS

LICHEN

it requires very low maintenance

grows on almost every surface and in many environmental conditions

it grows very fast it helps in cleaning the environment (air pollution)

they are not plants (don’t have roots to absorb water or other nutrients - nutrition photosynthesis) may experience a complete loss of body water in dry periods

cons

shady locations (it doesnt like sun)

grows very slowly (0.5mm to 500mm per year)

acidic soil (pH from 5 to 6)

some of them are sensitive to the presence of air pollutants

it requires a lot of moisture it gains its nutrients from the object that it’s residing on (it will remove colour of the building or the roof throughout the years)

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Lichen The next choice was lichen. It is a combination of fungus living in a symbiosis with algae or cyanobacterium - sometimes both. Fungi needs to take the food from outside sources whereas algae or cyanobacteria can conduct photosynthesis.

As an addition to all of the benefits vegetation has in society and urban space, it is very important to mention how green areas can affect an individual’s mental health. According to studies, being around plants helps people concentrate better and makes people happier and less stressed. ²

According to live science, it covers about 8 percent of the earth’s surface, and is found in many extreme conditions. Lichen can grow on stone, trees or glass, basically any kind of surface. And according to Robert Lücking, this comes as a result of the symbiosis between fungus, algae and cyanobacteria. ¹

To conclude, both moss and lichen have many advantages and disadvantages. In this case, for the urban scale project in Barcelona, we have decided that lichen is a more appropriate material. Of course, in the further development of this project both options remain possible. The point of (poro)city is to create a valid system for sound dampening that can be modified according to different locations and environments where maybe moss will be a better alternative to the climatic zone.

When in the woods, it is an indicator of the dead trees, however this is not a result of lichen taking the tree’s nutrients. As already mentioned, algae produces food for the plant through photosynthesis.

Lichen requires moisture but can survive a long period without it, which makes it perfect for our case study in Barcelona.

All the sound properties are very similar to the moss, in fact a lot of species have the moss part in the name. For example, Reindeer moss.

In the current market, it is very likely to find moss panels that are actually lichen. Lichen comes in many colors which are more appealing to the eye than the moss. However, unlike the moss, lichen is easily affected by the polluted environment and needs a lot more time to grow.

**there was not enough time to grow the moss and lichen due to the term duration and these experiments still have to be done in further development of the project. ¹ Bisco Werner 1996; Brethour 2007; Frank 2003; Pohmer 2008; Serwach 2008; Shibata, 2001, 2004; Yannick 2009 ² What Are Lichens? Article written by By Aparna Vidyasagar - Live Science Contributor, research taken from Robert Lücking, curator at the Botanical Garden and Botanical Museum in Berlin, Germany, and research associate at the Integrative Research Center at the Field Museum in Chicago.

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On the left side you can find a couple of Lichen species that can withstand the hot Spanish climate. Even though a lot of species can be combined in one place, we chose only two species to continue working with. Xanthoria parietina and Ramalina farinacea.

Xanthoria parietina is often called ‘common orange lichen’, ‘yellow scale,’ ‘maritime sunburst lichen’ or ‘shore lichen’ as it can be found near the Mediterranean shore. Typically on walls or rocks. On the mainland, it can be found on tree bark. The whole body of lichen is smaller than 8cm. The upper surface of Xanthoria parietina is a yellow or orange shade whereas the surface on the bottom where we can find rhizomes is white.

Ramalina farinacea is characterized by its long narrow branches which is why it often remains as small bushes. To add, just like Xanthoria parietina it prefers Mediterranean climate and can be found at low elevations on trees and shrubs. Unlike the Xanthoria parietina, Ramalina farinacea has the same colour on both sides. Even though it might look like a big plant in the images, it is not. Its branches are approximately 3mm wide and up to 70mm long.

Finally, the option of adding new species still remains optional. Due to the term duration and lack of time, there was no opportunities to further research on more types that could help to develop microhabitats.

As already mentioned, lichen can survive all kinds of environmental changes. This is why the thickness of the thallus (1vegetative part of the lichen that can develop into a morphologically diverse range of structures) can change depending on the habitat. They are thinner in shadows and much thicker in sunny areas. This comes as a result of algae not tolerating very intense light. In addition, it is very important to mention that the outer skin of Xanthoria parietina is packed with fungal hyphae. This protects thallus from water loss.

1Lichen thallus types, A.J. Silverside 2 https://www.youtube.com/watch?v=ymtIT8XIIEM Wild Food : Ramalina farinacea - a lichen 3 Nature spot webpage -Cartilage Lichen - Ramalina farinacea Images: https://liquensdebarcelona.wordpress.com/2017/03/29/

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One of the biggest advantages of adding lichen to this project was creating a microclimate.

Except for its sound-absorbing properties, lichen has so much more to offer. It contributes to the Earth’s biological diversity. There are more than 13 500 identified lichen species all over the world. According to the source, lichen plays an integral role in keeping our natural world working by providing food, cover, and nesting material for a variety of songbirds, mammals, and insects. ¹ To add, many humans use lichen as food or for medical purposes.

Even though many will interpret the presence of insects and small animals as a bad thing, it adds another level of complexity to the project. It starts to integrate into nature and bridge the gap between urban areas and nature.

Nowadays, everyday life is getting busier and busier and people don’t have time to spend in nature. By creating a green oasis in the city centre, this project will create a space that will be very beneficial. Numerous studies have shown that being in nature benefits your health as it helps decrease the levels of stress, improves memory, and helps sleep. ² Even if people are in a hurry, they will be forced to walk through the structure and will be exposed to some sort of nature for at least a short period when they are going to work or coming back home. With the help of (poro)city, people will finally be able to get lost in the music created by birds without feeling any guilt.

¹The Secret Life Of Lichens, In Exhibits by Cambridge Butterfly Concervatort, November 24, 2016 ²Spending at least 120 minutes a week in nature is associated with good health and wellbeing Mathew P. White, Ian Alcock,James Grellier,Benedict W. Wheeler, Terry Hartig,Sara L. Warber, Angie Bone, Michael H. Depledge & Lora E. Fleming

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zoomed in texture

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Surface texture Considering the sound properties, the next experiments were with the cork unit textures. As an example, concert hall Elbphilharmonie in Hamburg, Germany is made out of 10 000 gypsum fiber acoustic panels with the irregular surfaces on the top.

In order to get the texture, there was one more possible way, CNC milling surface taxture on the sheet before cutting the outlines of the units.

However, milling takes much more time which makes the whole fabrication process inefficient.

Textures were created in order to make the units more efficient for sound dampening. As the surface is uneven, the sound waves reflect similar to the Schroeder diffuser, where they break into smaller waves and reflect at different times and different directions which reduces the sound.

Considering cork is not the only material, as lichen would be added to the surface area of the unit, it made no sense to add the textures as the lichen would cover the texture and efficiency would be minimal. As already mentioned in the material chapter, lichen can grow on almost any kind of surface, even on glass, so it didn’t really make any changes for the lichen if the surface was smooth or had some specific texture on it.

These textures were created by using the Kraft-pulping technique. To be more precise, according to Javier Fernández-Rodríguez and Jalel Labidi, Kraft-pulping is a treatment of wood chips in a boiling mixture of water, sodium hydroxide and sodium sulphide that break the bonds between lignin, hemicellulose and cellulose. After this procedure, the cork was left to dry.¹

To conclude, it was decided not to add texture the the surface of the cork as it added a lot of time in the fabrication process and because the addition of lichen would add a level of texture to the unit.

Once the cork experiments dried, they became very stiff and fragile which resulted in them being very breakable.

¹Lignin Separation and Fractionation by Ultrafiltration Javier Fernández-Rodríguez and Jalel Labidi, in Separation of Functional Molecules in Food by Membrane Technology, 2019

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Binder Poro(city) is an urban scale project made for dampening the sound in public spaces. As the main idea was to create porosity of the structure by aggregating cork units, we tried to find a way to stick the small units together so that the external influences such as wind wouldn’t harm the structure and prevent the units from falling.

Natural rubber is one of the most flexible rubber types and it is resistant to water and certain chemicals. To add, it is resistant to cutting, tearing, and chipping. Nevertheless, it has a lot of tensile strength and adheres easily to other materials. This is very important in our case as the rubber is used for binding purposes.

As all of the materials used until now were very sustainable, our wish was to keep all the materials sustainable. It was very hard to find natural binding material that would be durable and wouldn’t melt or rot such as beeswax.

On the other hand, natural rubber is vulnerable to fuel and oil. Even though it is not resilient to heat, the most ideal temperature range while using natural rubber as a material is between -55 degrees Celsius and 82 degrees Celsius which is enough for it to withstand Barcelona’s climate.

After a couple of tests, we found out that natural rubber was the best choice. Natural rubber often called Latex is harvested from a family of trees called Euphorbiaceae. Although there are around 200 plants in the world producing latex, most of the world’s latex comes from a tree called Hevea brasiliensis, widely known as the rubber tree.

Natural rubber is extracted with a method called tapping. By making incisions in the bark and collecting the fluid into vessels attached to the rubber trees. The extracted product is a sticky, milky sap.1 The latex is then transferred to collecting tanks and from this point, the process is determined by its destination. It can be converted into concentrate, coagulated, sheeted or crumbed, dried, or baled for use as a dry rubber.

Considering the structure, natural rubber is a polymer of isoprene (also known as 2-methylbuta-1,3-diene) with the chemical formula (C5H8)n. To put it more simply, it’s made of many thousands of basic C5H8 units (the monomer of isoprene) loosely joined to make long, tangled chains. These chains of molecules can be pulled apart and untangled easily, but they spring straight back together if you release them—and that’s what makes rubber elastic. 2

digital matter | intelligent constructions

¹Natural Rubber - From A Gooey Sap To A Usable Material - Bob Jackson Natural Rubber Adhesives - K.F.Gazeley, W.C. Wake ²Rubber - Chris Woodford Natural Rubber: Structure and Function-By D.J. Miller Valuable source - Mechanical and Corrosion-Resistant Properties of Plastics and Elastomers By Philip A. Schweitzer

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100% Natural rubber

100% Natural rubber + 5g CaCO3

100% Natural rubber + 5g clay

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For our experiments, we tried 60% ammoniated natural rubber (100g) on its own and in composites with clay(5g) or CaCO3(5g and 10g).

To begin with, 100g of 60% ammoniated natural rubber was not the right choice as the two cork units split not long after applying pressure to it. In this case, the binder sticks much better on some uneven structure than the smooth one.

Second option was a composite of 60% ammoniated natural rubber (100g) and clay (5g) as it has good binding properties. The result we got is a much stronger but also very brittle binder. In our case, when applying pressure to it, units broke almost immediately. To resolve these issues, there is a possibility of adding a softener such as glycerine.

Finally, we tried to combine 100g of natural rubber with CaCO3. Calcium carbonate is often used as a fertilizer for plants. One of its advantages is rising the soil pH. Besides, it is increasing the efficiency of other nutrients.

Sometimes the nutrients that a plant craves might be present in the soil but unavailable to it if the pH is not right for the plant to easily take the nutrients it desires.

This experiment showed CaCO3 makes the binder much weaker and thicker. After applying pressure to two cork units connected with the Latex-CaCO3 composites, the 5g one was very firm whereas after some time the 10g one started to weaken. The units did not split completely but the binder started lingering. Also, CaCO3 created small bubbles in the texture and made the binder dry much faster.

In the end, it was shown that 60% ammoniated natural rubber (100g) with CaCO3 (5g) was the best option for the purpose of binding cork elements.

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Sound tests Sound test 1

3cm

diffusing cork panel 2cm

100cm

less reflective material /cork/

diffusing cork panel

98cm

50cm

less reflective material /cork/ panel condenser microphone

1cm

speakers 50cm

50cm

50cm

30cm

Equipment:

Condenser microphone

Audio Interface

Audio recording (quicktime) Speaker

Cork Diffuser Panel Environment: The experiment was done in an empty room with hard, reflective surfaces.

Parameters: The speakers were placed 500mm from the panel and the microphone was placed 500mm behind the speaker. A range of frequencies was recorded in the empty room, and repeated with the cork diffuser panel at equal loudness.

Frequencies tested: 125, 250, 500, 1000 and 2000 Hz.

base

First test was made with the regular diffusion panel and pile of cork units.

At the end, the graph on the right shows that the aggregated pile was more efficient than the panel in all of the frequencies except the minimal, 125 Hz one.

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dB level 125Hz

dB level 500Hz

sound level (dBa)

sound level (dBa)

time

time

dB level 250Hz

sound level (dBa)

sound level (dBa)

time

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Sound test 2

cork + moss

3cm

cork

100cm

less reflective material /cork/

50cm

aggregation model of 7 units

less reflective material /cork/ panel

100cm

1cm

condenser microphone

speakers

50cm

50cm

base

30cm

Equipment:

Condenser microphone

Audio Interface

Audio recording (quicktime) Speaker

Pile of cork units (7) Moss Environment: The experiment was done in an empty room with hard, reflective surfaces.

Parameters: The speakers were placed 500mm from the cork units and the microphone was placed 500mm behind the speaker. A range of frequencies was recorded in the empty room, and repeated with the pile of cork units, and the pile of cork units with moss, at equal loudness.

Frequencies tested: 125, 250, 500, 1000 and 2000 Hz. This sound test was made with the cork pile without the moss versus the cork pile with moss on the structure. It shows that moss helps the sound dampening and reverberation time is noticeably lower.

To conclude, these tests show the materials and chosen approach were the right way to go. It showed that the new approach of the aggregated cork structure with the vegetation on it was more efficient than the standard panels we know. ** These tests were made before the transition from moss to lichen. Due to the lack of equipment the sound tests couldn’t be redone physically but only computationally which can be seen in further chapters.

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dB level 125Hz

dB level 500Hz

sound level (dBa)

sound level (dBa)

gradient difference 0.6

gradient difference 0.6

time

time

dB level 250Hz

dB level 1000Hz

sound level (dBa) sound level (dBa)

time

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gradient difference -1.48

time

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Aggregation as a sound dampening technique As already mentioned, porosity is the main focus in this project while combattiing noise pollution. It is why some of the materials are better in sound absorption than others.

Porous materials are composed of cracks, cavities and all kinds of channels that allow the sound waves to enter the material. For absorption to happen, cavities have to be exposed to the environment.¹ When a material is exposed to sound waves, the air molecules at the surface of the material and in between the pores are forced to vibrate and in that way, lose some of the energy. It happens because part of the energy of air molecules is converted into heat, due to thermal and viscous losses inside the material.² Taking into consideration that the porous structures are the most efficient in reducing the noise, the next most logical step was to recreate the porosity in the bigger scale. Aggregation came as the best approach for this situation.

There are numerous definitions to explain what the aggregation really is.

According to Nedderman, the best way to describe aggregation is as a large amount of elements in loose contact. ³ And, according to Dierichs & Menges, it can be described as a large arrangement of loose elements that are observed and modulated by the architect on the particle or system-level to perform one,or more typically architectural tasks. 4

¹ Recent Trends in Porous Sound-Absorbing Materials by Jorge P. Arenas and Malcolm Crocker ² Porous materials for sound absorption by Leitao Cao, Qiuxia Fu Yang Si, Bin Ding, Jianyong Yu ³ Nedderman, 1992, 1; Duran, 2000, vii 4 Dierichs, K., Menges, A.: 2010, Material Computation in Architectural Aggregate Systems, in Life In:Formation: On Responsive Information and Variations in Architecture, Proceedings of the 30th Conference of the Association For Computer Aided Design In Architecture (ACADIA), New York City, pp. 372_78.

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In the most simple explanation, aggregation is stacking a big number of the same elements based on the gravity. For instance, the most well known example found in nature of the granular aggregation is snow. Snowflakes fall on the ground without any rules or order and stack in a pile as a result of gravity.

The main beauty in aggregation is that the product is never the same, and can be recreated in millions of ways. As Karola Dierichs and Achim Menges from ICD Stuttgart said “The capacity of these loose arrangements lies in their ability to continuously adjust to changing system-external and system-internal influences.”5 Therefore, the potential of the design is endless.

In addition, the aggregated structure would create perfect dark spaces in the gaps between the units for lichen to grow. As a reminder, lichen prefers to grow in a shadow where the sun is not drying it up and the aggregated structure is creating the perfect environment for it to live, well satisfied.

There are many factors that can affect the aggregation process and the structure itself. During our research we took into consideration six main factors: 1: unit design 2: the speed of dropping or throwing of the unit 3: number of units dropped or thrown at once 4: angle from which the unit can be dropped or thrown 5: volume created with specific number of units and 6: the height in which the units are thrown

5 Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018

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STOCHASTIC

DETERMINISTIC

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Stochastic vs deterministic approach There are two main techniques when it comes to the construction of an aggregated system. Elements can be assembled in a stochastic or deterministic way.

Piling up the elements stochastically means to throw or drop units into a pile without any order or rules. With this approach, most of the time the units are identical to one another. The outcome of this approach is therefore unpredictable. The advantage of this is the production,fabrication and assembly time.

In opposition, a deterministic approach is designed and organised with a set of rules. Intersection occurs either by very well designed joints, or predetermined or specifically placed units. All the units can be different and are designed to the smallest details. Automatically, it means the fabrication time is much longer and the assembling process is much more complicated. The positive side of this approach would be that there is more control over the final outcome of the structure.

For our design in particular there was a need for a deterministic approach as the project was made to dampen the sound. Because of that, noise sources of the site had to be mapped and taken into consideration while designing the structure. However, gaps between the units piled up in a stochastic way created a better environment for the sound to redirect.

Poro(city) is the project made in between both stochastic and deterministic ways of aggregation. It compiles the best of both in order to create the most efficient hybrid for dampening the sound in the environment.

The aggregation is stochastic whereas the overall shape design is more deterministic.

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AGGREGATION PAVILLION

ROCK PRINT PAVILLION

Aggregation Pavilion was made by the Institute for Computational Design in Stuttgart, Germany. It is one of the most important research papers made on the topic of aggregation.

Rock Print Pavilion by Gramazio K. was made as a part of ETH Zurich research. The structure was made of tiny loose stones placed by robot so they interlock perfectly with each other.

Also, it is the first fully enclosed architectural space completely constructed from the small designed units which lie in loose contact. Gaps inside the structure were constructed with the help of balloons.

To make sure they don’t move they were jammed together with tiny strings.

The bottom part is wider as a result of construction needs.

The whole structure was made with 120 000 star-like particles. Everything was assembled with the robotic hand as the main tool.

Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018

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BARTLETT CLUSTER 4

PUZZLING

Bartlett Cluster 4 is an ongoing research line made by Bartlet UCL. Furniture was made out of moulded unit in 3 different sizes.The elements were made in two pieces which allows them to be hollow and lightweight.

Puzzling by Anton Alvarez is a project generating plenty of elements such as lamp with one single wooden module. The module has been industrially multiplied into thousands.

Connection is made by the intersection of one unit into another. The whole structure was made with a robotic arm assembling the pieces.

The advantage of this project is that the units can be joined without glue. In addition, the elements can be assembled by humans simply by combining the units into eternal repetition.

Design Computation Lab, UCL, RC4 -Mickeymatter, tutors: Gilles Retsin, Manuel JimĂŠnez GarcĂ­a with Vicente Soler students: Panagiota Spyropoulou, Hyein Lee, Pooja Gosavi, Pratiksha Renake

Image Source: Marcus Abrahamson

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Fabrication According to Opendesk, digital fabrication is a type of manufacturing process where the used machine is controlled by a computer.š Machines available right now for the fabrication are CNC milling machine, 3D printer and laser cutter.

For this project, it was used CNC milling machine as it is the easiest and the most efficient way to fabricate a huge amount of cork units. The laser cutting machine was too weak to cut the thicker sheets of cork and 3D printing in general requires way too much time. In addition, with the cork as a material it would have to be made into pulp in order to print it.

To add, moulding cork was one more way to fabricate the units. However, it wasn’t the efficient way as there is a big number of units. It requires more hands and in that way more time.

Considering the production process of the unit relevant factors were: 1: nesting the units and 2: fast assembling

1Opendesk image source: 3D printing / 3D printing today webpage/, cnc milling machine /pinterest/, laser cutter /Custom Made-special

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Design parameters Cork as a material is very fragile so while designing the unit it was extremely important to take this into consideration. As for the aggregation, units have to be designed well enough to interlock with each other and create a structure that can be tight enough, even without the binder.

By exploring the work of ICD Stuttgart1, we came to the conclusion that the star typology works really well with the aggregation and started developing it further. It was very important to modify the typology to the unit material, cork, and also to the sound dampening properties.

In order for sound to get reflected as much as possible, there had to be enough of the different angled surfaces in the structure. In that way, the sound waves would bounce and redirect much more while decreasing their energy levels. To add, cork can often be heavy, especially when you add layers and layers which is the exact case in aggregation. It is easy to assume that the units would break. As a result of this, there had to be one more aspect while designing the unit - maximum load displacement.

Finally, there were nine factors that needed attention for the unit to be perfected: 1: leg length 2: core size 3: thickness of the cork 4: number of legs 5: efficient material consumption (minimum unit volume) 6: maximum pile volume, 7:maximum load displacement 8: unit weight and 9: optimal surface area for lichen to grow on

For the structure to be as profitable and easy to fabricate as possible there was a significant importance in balancing the maximum pile structure and least material consumption.

1Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018

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thickness: 10mm fab. parameters: 6mm drill bit - Shopbot CNC Machine time: approx. 50 min per sheet / 10 per 915x615 sheet dimensions: 200x200mm tolerance: 10mm

thickness: 10mm fab. parameters: 6mm drill bit - Shopbot CNC Machine time: approx.60 min per sheet / 10 per 915x615 sheet dimensions: 200x200mm tolerance: 10mm

thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.40 min per sheet / 6 per 915x615 sheet dimensions: 300 x 300mm tolerance: 20mm

thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.40 min per sheet / 24 per 915x615 sheet dimensions: 150 x 150mm tolerance: 20mm

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The first experiment was the star shape typology unit fabricated in two pieces. The pieces were connected together by the joinery in the middle of the unit core.

By changing the parameters such as thickness of the cork or leg length, other parameters such as volume started to change. As seen on the picture on the left, Geometry 1 and Geometry 2 have all the parameters the same except that Geometry 1 has shorter and thicker legs than Geometry 2.

As a result it is obvious that Geometry 1 creates bigger volume even if the number of units is the same (30). This is due to the fact that Geometry 2 was designed wth longer legs. When it is aggregated, the whole shape lengthens and starts to aggregate in different way. In addition to this, the unit got weaker as the legs were very narrow and caused cork to break.

While milling the cork sheets for the Geometries 1 and 2, a 6 mm drill bit was used which took approximately 50 mins for 10 units. In order to make it more efficient, Geometries 3 and 4 were drilled using a 8 mm drill bit. As a result the milling time got shorter by 10 minutes.

To conclude, these tests showed that the best units to aggregate were with the Geometry 1 as the balance between the volume and the material consumption was the best. Nevertheless, the aggregated pile still did not create the best environment for the sound to reflect as much as wanted.

The result to this were gaps too big to redirect the sound in the desired way. To add, it was very difficult for lichen to grow as there was not enough surface for it to grow.

Geometry 3 and Geometry 4 are much thicker, instead of the regular 10 mm thickness, the thickness of the units is 20 mm. This gives enough strength for legs not to break. The two geometries are perfectly symmetrical and have peak point at the end of each leg in order to aggregate better. Finally, the test showed that even with the modification, the unit didn’t aggregate creating a bigger amount of volume but more cork was consumed. To add, the two geometries are made in different sizes, Geometry 3 is 150x150mm and Geometry 4 is 300 x 300mm which didn’t cause any changes in aggregation, except that the aggregated pile of the smaller unit (Geometry 3) was smaller.

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thickness: 10mm fab. parameters: 6mm drill bit - Shopbot CNC Machine time: 50 min per sheet / 10 per 915x615 sheet dimensions: 200x75mm tolerance: 10mm

thickness: 10mm fab. parameters: 6mm drill bit - Shopbot CNC Machine time: 60 min per sheet / 10 per 915x615 sheet dimensions: 200x150mm tolerance: 10mm

thickness: 10mm fab. parameters: 6mm drill bit - Shopbot CNC Machine time: 50 min per sheet / 10 per 915x615 sheet dimensions: 160x75mm tolerance: 10mm

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In the next experiment there was a new approach that would offer much more surface area for lichen to grow. The 4 geometries on the left (Geometry 5, Geometry 6, Geometry 7 and Geometry 8) are chosen from a bigger collection and are the best examples to explain the thinking process of the unit design and help come to a conclusion.

The main idea behind these units was to use a hexagon as a base. The thought behind was for the 6 edges of the hexagon to help with stacking.

The main difference between Geometry 5 and Geometry 6 is the “legs”. In Geometry 5, the legs are squared and in Geometry 6, they are hexagons whereas Geometry 8 was created by two hexagons interlocking.This Geometry worked the best as the fabrication was the most efficient. The fabrication time was shorter and the assembling was much easier than other units.

Unfortunately, this method wasn’t the final direction. The units were not aggregating vertically but more horizontally, on the ground. Elements, especially Geometry 6 acted like small cork balls. The final volume was not optimal considering the amount of cork used.

The nesting was good, but in order to produce one unit, a big amount of material was consumed. Automatically, this requires much more fabrication time.

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thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.70 min per sheet / 20 per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.60 min per sheet / 30 per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.70 min per sheet / 20per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

thickness: 20mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.75 min per sheet / 10 per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

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The next set of geometries, 9, 10, 11 and 12 are very geometrical. Geometry 9 and 10 have 4 legs and are being assembled by the joinery in the middle.

Geometries 11 and 12 have a base with a gap on which legs are being attached. The gaps are here to allow the leg of another unit to come inside and stack better.

The small connection between the base and the leg in Geometry 11 is making the unit fragile whereas Geometry 12 has been modified without that small piece. Still, because of the big number of regularly placed vertical legs, this Geometry was not the right way to go.

The main problem of these geometries besides the small surface area for lichen to grow is even though the thickness is 20 mm, the legs are very fragile and units would progressively start to break. To add, Geometry 9 and 12, are aggregating in a more deterministic way than the stochastic one.

The nesting is pretty good as all the unit parts are very thin. There was not much cork wasted.

The volume created was satisfying. The ratio of the material spent and volume was decent.

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thickness: 10mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.50 min per sheet / 10 per 915x615 sheet dimensions: 400x300mm tolerance: 10mm

thickness: 10mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx. 40 min per sheet / 3 per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

thickness: 10mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: approx.40 min per sheet / 5 per 915x615 sheet dimensions: 370x400mm tolerance: 10mm

thickness: 10mm fab. parameters: 8mm drill bit - Shopbot CNC Machine time: 40 min per sheet / 5 per 915x615 sheet dimensions: 300x300mm tolerance: 10mm

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Through the unit design process we came to the conclusion the first type was the most efficient one. From there we tried to modify the unit as much as possible to make it the most efficient.

Because of the small hooks on the legs, units are stacking very well. The main difference between these geometries (Geometry 13, 14, 15 and 16) is the number of surfaces attached to the base in the middle (from 4 to 8) as well as the number of legs per each surface. Geometry 13 has five legs whereas Geometry 14 and 15 have four legs per surface. Last but not least, Geometry 16 has only three legs per surface.

As a result of many legs and surfaces Geometry 13 ended up as too heavy, and not optimal in the fabrication process. The time of one single unit fabrication was too long and material consumption was huge.

During the optimisation process the Geometry 15 ended up as the perfect one. It has four surfaces with four legs. Nesting is optimal, there still is a bit of lost material but an advantage of using sustainable material such as cork is that the leftovers can be reused and a new set of production sheets can be made. In addition, it aggregates the best. It creates the most volume, the gaps between units are not too big.

Last but not least, the optimisation process gave us the units with the legs wider near the core but more narrow at the end which makes the units stronger.

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Computational optimization Evolutionary algorithm (EA) is a generic population-based metaheuristic optimization algorithm. An EA uses mechanisms inspired by biological evolution, such as reproduction, mutation, recombination, and selection.

Candidate solutions to the optimization problem play the role of individuals in a population, and the fitness function determines the quality of the solutions. Evolution of the population then takes place after the repeated application of the above operators.

A few feautures of the evolutionery solvers are helpful to know. It is important to realise that the procedure keeps track of several solutions eather than maintaining just one, best solution found so far. This population of solutions develop orevolves, in steps that mimic naturally occuring evlutionary process. From the population of solution that is builds and maintains, the procedure can generate new solutions, following the principle that an offspring solution should combine traits from each of two paretn solutions.¹ Wallacei is an evolutionary engine that allows users to run evolutionary simulations in Grasshopper 3D through utilising highly detailed analytic tools coupled with various comprehensive selection methods to assist users to better understand their evolutionary runs, and make more informed decisions at all stages of their evolutionary simulations; including setting up the design problem, analysing the outputted results and selecting the desired solution or solutions for the final output. Additionally, Wallacei provides users with the ability to select, reconstruct and output any phenotype from the population after completing their simulation.²

In this project, we used Wallacei to find the most optimal unit for aggregation. The main objectives used were leg length, minimal mesh volume and maximum load displacement as they are the top three important factors for the units. Leg length and maximum load displacement are for strength and best possible aggregation whereas minimal mesh volume is here in order for the unit not to be very heavy and material consumption reasonable.

There are a lot of requirements this unit had to fulfill. The whole optimization process took a very long time. After every Wallacei simulation, there had to be done big number of tests in order to make sure the unit was the right one and requirements such as good interlocking properties, easy fabrication, structural stability and sound dampening properties were achieved.

After the tests would be done the process would start again and again based on its blind spot.

Parametric unit design - Wallacei optimization and finally - properties analysis until the perfect unit was chosen.

¹Optimization Modeling with Spreadsheets,By Kenneth R. Baker ² www.wallacei.com/about

Pareto Front Solutions Area

Top 5 Leg Length Fitness Objective Values

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Sound propagation is dependent on many factors, such as temperature, atmospheric pressure, frequency, interaction with other sound waves and the impedance of its medium to name a few. It is difficult to predict or simulate it’s movement and physical testing is needed to find optimal thicknesses, geometries and orientations of the aggregations.

A unit of units can be fabricated off site by simulating the soundscape of the site and dropping units based on microphone readings. On site, temporary sensors can be placed during construction to determine areas where more units are needed.

A flexhopper simulation loop was created to visualize the dropping of units based on the amount of sound rays intersection with a mesh grid. The two mesh grids of 3x3 faces record the location of ray intersections and determine the new drop points based on the 2 columns with the most sound passing through.

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Material layering and fabrication

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Impedance matching Specific acoustic impedance is a measure of a medium’s resistance to sound flow. It is determined by the ratio of the complex amplitude of sound pressure to the complex amplitude of particle velocity. It’s inverse, Admittance, is a measure of the sound flow through the medium.

For an estimate of the sound attenuation of the material, only the impedance normal to the surface needs to be considered. The impedance will then follow the equation:

Z0 = đ?œŒ0 Ă—đ?‘Ł0

Where đ?œŒ0 is the density of the material and đ?‘Ł0 is the speed of sound in the material.

The relationship between the impedances of two materials will determine the amount of reflected and transmitted wave from the incident sound wave. To reduce transmission, a larger impedance difference or mismatch is needed. To reduce reflection, the impedances should be as similar as possible.

Air has a very small impedance of about 0.0004 Mrayl. Solid building materials will have higher impedance values, resulting in an almost completely reflected sound wave. Materials with lower densities or speed of sound will allow more transmission and reduce the reflected amount of the sound wave.

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Due to it’s impedance mismatching with air, a single material system will either be a good sound absorber or a good sound barrier, but not both. A material with large surface reflections will have larger transmission losses, but poor absorption. A material with good transmission will absorb more sound, but the transmitted wave will be transferred through the material.

A multi layered material system can be designed for both absorption and transmission loss. Materials can be selected based on their impedance values, with smaller to higher mismatch as the sound travels through the system. This will allow more of the wave to enter the materials, for then to be reflected off the backing plate with the highest impedance mismatch.

A layer of air between the material layers will increase the impedance mismatch. This reflects more of the sound back into the material at the intersection at the intersection of the material layer and the air gap, and has been shown to increase the efficiency of layered acoustic panels*.

Our material system is a layer of moss/lichen, expanded cork and plywood.

The moss/lichen scatters and absorbs the incoming sound wave and the sound reflected from the cork layer. The cork absorbs a large portion of the sound, which is dependent on its frequency. The air gap between the cork and the plywood reduces the transmitted wave from the cork and increases the reflection from the plywood, which will reflect the sound back through the layers again.

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Going into how sound would be affected by these materials.

Specific acoustic impedance is a measure of a medium’s resistance to sound flow. The relationship between the impedances of two materials will determine the amount of reflected and transmitted wave from the incident sound wave.

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The lichen scatters and absorbs the incoming sound wave and the sound reflected from the cork layer.

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The cork absorbs a large portion of the sound, which is dependent on its frequency.

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The air gap between the cork and the plywood reduces the transmitted wave from the cork and increases the reflection from the plywood

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Passeig del Born The heart of Barcelona’s Born district, the Passeig del Born is a long rectangular open space which stretches from the Santa Maria del Mar church to Placa Comercial.

In medieval times the Passeig was the scene of jousting competitions, but today the (k)night life is a little more contemporary. Arousing from a typically sleepy afternoon, the shutters are pulled up and suddenly both sides of the street are lined with cool bars, such as the popular Miramelindo, and funky eateries, such as Crepes del Born.

Hipsters arrive on their scooters to hang out with tapas and a caĂąa or two, whilst touts sell 1 euro beers to Bohemians and hard-up tourists content to drink from the comfort of stone benches.

https://www.barcelona-life.com/passeig-del-born

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Site characteristics Atmospheric pollution is not the only type of contamination that is harming living beings on the planet. According to the World Health Organization (WHO), it is one of the most dangerous environmental threats to health.

And according to the European Environment Agency (EEA), noise is responsible for 16,600 premature deaths and more than 72,000 hospitalisations every year in Europe alone. Drivers honking the horn, groups of workers drilling the road surface, aircraft flying over us in the sky... Noise, noise and more noise.

In Barcelona, the effect of noise is further aggravated by high concentrations of people living together (30,000/km²). The noise pressure comes from road traffic, air traffic, railways and construction activity and leisure activities.

Cities have become the epicentre of a type of pollution, acoustics, which, although its invisibility and the fact that coronavirus crisis reduced it until almost yearn it, is severely damaging to human beings. So much so that the European Environment Agency estimates that noise is responsible for 72,000 hospital admissions and 16,600 premature deaths every year in Europe alone.

Over half of Barcelona’s population is subjected to noise levels over 65 decibels which can be defined as a harmful environment, during the entire day (0800-2200 hours) which explains why locals have to shout to make themselves heard.

Not all sound is considered noise pollution. The World Health Organization (WHO) defines noise above 65 decibels (dB) as noise pollution. To be precise, noise becomes harmful when it exceeds 75 decibels (dB) and is painful above 120 dB. As a consequence, it is recommended noise levels be kept below 65 dB during the day and indicates that restful sleep is impossible with nighttime ambient noise levels in excess of 30 dB. There are many sources of noise pollution, but here are some of the main ones:

The province of Barcelona is host to some 1,900,000 vehicles, representing a ratio of 0.4 vehicles per inhabitant. Tourists in the other hand,frequently stay late into the night playing music in the squares.

In this case study, we tried to tackle noise pollution in areas that the sources are usually related to leisure activities, such as bars, pubs, and restaurants, as there is no specific zoning for the residential areas and restaurants, there are many people in Barcelona affected by noise pollution.

Looking at the data from polluted areas like Carrer de Valencia or the Cathedral of the holy cross and Saint Eulalia and Passeig del born, we chose the last option because of the number of people accommodating in this area.

Traffic noise Air traffic noise Construction sites Catering and night life

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Spring Rose.png 6/21/2020

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Analysis Wind Analysis Based on the previous studies on the effect of weather on sound traveling, the analysis for the site got into more depth in general, wind affects the speed of sound propagation, which affects the sound intensity.

In this wind analysis, in Passeig del born, we can understand that the strongest wind speeds in this location are during Spring and Summer months from the North and South so more people will be out and about during these seasons, therefore we assume the intensity of the sound will be stronger.

The charts indicate that in winter the area is calmer for 5.97% of the time which is about 127 hours, and about Spring and summer, respectively the calmness of the area is 15.93% and 7.60%. This means 350 hours for Springs and 167 hours in Summers. About Autumns the street is calm for 5.61%, and tha means 187 hours.

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•

Radiation is predominantly from the South • •

Possible solar collectors in design How much sun the moss will need/not •

•

Potential shading on the site

Higher temperature = higher kinetic energy for air molecules = sound propagates faster = higher intensity

Velocity = 331 + 0.6 * Temperature Intensity = Pressure * Velocity

Total Radiation

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Spring Sunlight Hours Plan.jpg

Spring Average of 8 hours of sunshine

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In another aspect of technical analysis, based on the data we made a section diagram of what are the sources and challenges that we have to tackle within this specific site.The height of the surrounding buildings and also the width of the site should have been considered.

Based on the strategic noise map we can understand how noise pollution increases as we get to the evening and hours that people in the residential part are resting.From 9 pm to 7 am the range of noise pollution stands between 65 to 70 dB, which is considered a highly polluted area in terms of noise.

Before implementing our design idea to the site we checked all the existing materials and their noise reduction coefficient. Most of the materials used in the facade of the buildings were stone and bricks and the coefficient for these materials, respectively are 0.2 and 0.05.

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Information extracted from: Mapa Estratègic De Soroll | El Web De La Ciutat De Barcelona. [online] Available at: <http://w20.bcn.cat/WebMapaAcustic/mapa_soroll.aspx> [Accessed 26 March 2020].

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As this is a project located in the very busy street, it was important to study the movement of the people. On the site, many streets intersect with Passeig del Born which means many people come from many different directions. The main and the busiest routes are the ones coming from Via Laietana and Carrer de la Princessa as these are the two biggest streets around the site. Carrer de la Princessa is connected to Passeig del Born with the street called Placeta de Montecada whereas Via Laietana is connected with numerous of smaller streets that follow up Carrer de Santa Maria.

Besides, Passeig del Born is very famous for its nightlife. The street is very wide and on each side, there is a big number of pubs one next to another.

This leads to people staying in the street for a longer period just going in circles from one bar to another. Also, during the summertime, it is not unusual to find a big amount of people sitting on the benches in the middle of the streets drinking and having fun.

Taking this into consideration, we didnâ&#x20AC;&#x2122;t want to overtake the whole space and leave people without their little place for entertainment but only to modify it.

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Computational optimization Based on the argumentation and site analysis, which was generally a back and forth design process we tried to propose a tensile mesh structure in which units can attach and stand on it. This idea was chosen because of the adaptability of it in many parts of the city and in the end, it will be easy to disassemble it and place it in some other area or even recycling.

Needless to mention, other than finding the anchor points for the net to be attached we needed to propose the most optimized shape. For this purpose, the evolutionary solver called Wallacei was used again.

Following creating the surface volume, populating the mesh was the second step. Since we already found the optimized unit for this aggregation in the previous part, afterward we created an aggregation of the optimized unit for sound dampening.

It is helpful to understand what the Evolutionary Solving method can and cannot do, and what each of the possible Solver Result Messages means for this method. At best, the Evolutionary method – like other genetic or evolutionary algorithms – will be able to find a good solution to a reasonably well-scaled model. Because the evolutionary method does not rely on derivative or gradient information, it cannot determine whether a given solution is optimal – so it never really knows when to stop. It knows only that a new candidate solution is “better” than other solutions found earlier.

Hence, the evolutionary method stops and returns a solution either when certain heuristic rules indicate that further progress is unlikely, or else when it exceeds a limit on computing time or effort that you’ve set.

When it comes to an evolutionary solver we need to set goals so the machine would run and iterate the possible generations related to those goals. In this case, two goals were set, first was the minimal mesh volume and at the same time maximum sound reduction.

Running the python code was also a necessary step to take since the raytracing and sound calculations are key for this process. This code would help us to reduce the sound and would create the site context at the end.

Prior to run the evolutionary solver, there were steps to take. Creating a box in the size of the unoccupied place in the street and then voids were created. these voids placed the base on the limitation in the site such as trees and the balconies of the building facades. then a mesh was crated by the grasshopper.

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Pseudo Code Diagram

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1. CREATE BOX

2. PLOT TREES AND MOVEMENT ROUTES

3. CREATE VOIDS

4. CREATE ISO SURFACE

5. MESH DIFFERENCE

6. POPULATE MESH

7. ORIENT UNITS TO MESH

8. CREATE NOISE SOURCES

9. ADD CONTEXT

10. RUN PYTHON

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FITNESS VALUES Objectives

The premise of an evolutionary algorithm (to be further known as an EA) is quite simple given that you are familiar with the process of natural selection. An EA contains four overall steps: initialization, selection, genetic operators, and termination. These steps each correspond, roughly, to a particular facet of natural selection, and provide easy ways to modularize implementations of this algorithm category.

Simply put, in an EA, fitter members will survive and proliferate, while unfit members will die off and not contribute to the gene pool of further generations, much like in natural selection.

EAs can also be extended to use multiple fitness functions. This complicates the process somewhat, because instead of being able to identify a single optimal point, we instead end up with a set of optimal points when using multiple fitness functions. The set of optimal solutions is called the Pareto frontier, and contains elements that are equally optimal in the sense that no solution dominates any other solution in the frontier.

A decider is then used to narrow the set down a single solution, based on the context of the problem or some other metric.ยน

ยน https://towardsdatascience.com/introduction-to-evolutionary-algorithms-a8594b484ac

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Best: min Height

Best: dB Reduction

Best: min Mesh

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Simulations were done to test the scattering directions of increasingly concave and convex curved geometries with equal number of units.

The results showed similar scatterings to solid concave or convex surfaces, with some irregularities due to the varying unit surface angles.

Concavity focuses the sound to the center while convexity scatters the sound to the sides. Alternating concave and convex geometries can control sound propagation and simultaneously scatter and direct noise away from buildings or other hard surfaces that can amplify the sound.

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Fabrication process Considering the fabrication process, the first initial thought was to prefabricate the whole structure, split it into pieces (units of units) and join them on site. After the final design was made, it was obvious that the most possible way of fabrication would be the one on-site. One of the biggest advantages of stochastic aggregation is that the assembling part is very easy and there is no need to overcomplicate it.

During the whole term, a big amount of attention was given to the unit design and how it behaves while aggregating. After choosing the right unit, there was no worry of how the “piling up” of the structure would happen.

Chosen unit aggregates very well because of the small hooks on the unit legs. Hooks work very well with the mesh as the legs of the unit pass through the gaps in the mesh and because of the hooks they stick together.

The first step of the assembling is attaching the mesh to the buildings.

After the mesh is attached the structure is being aggregated. Aggregation is happening with the crane throwing units on the mesh from high above.

The whole “piling up” process is split into several layers. The first layer are the biggest units, the second slightly smaller ones and the last, the third layer are the smallest units. In this way, the structure is very dense which helps sound dampening. All the units are joined together with natural rubber and calcium carbonate binder. The binder, as well as the lichen, come in between every layer.

The only prefabricated parts are CNC milled and assembled units along with a knitted net. These parts are then transported on site.

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Four details are connecting the structure to the site. However, there are always limitations when it comes to urban infrastructure.

Many layers must be taken into consideration as the municipalityâ&#x20AC;&#x2122;s law is different in every city and country. In Barcelona, there were strict laws regarding the manipulation or attaching such a big design to the facades.

As a result, we found several strategic places where we could attach our mesh. To the top of the buildings where it doesnâ&#x20AC;&#x2122;t bother anyone, to the ground and last, but not least, to the balconies.

These connections are in three different levels so it assures that every part of the structure is well connected. The heights of the details are going from 0.00m to 21.00m which is the highest building on the site. Other buildings are around 18m high. Connection to the balconies is most often on the first or second floor which makes it in the same height as the hanging structure.

Exceptions are possible if required by engineers.

Details are designed to be very simple and elegant. They consist of metal parts, screws and wires. The whole structure is in tension all the time.

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Drawings

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Conclusion Looking through the possibilities of Poro(City), we came to an understanding of how this design can be implemented in many parts of the city, as the zoning of urban cities are disappearing and with the population increase, the need for a solution as urban infrastructure, tackling growing noise pollution will arise more. In these days, where almost every family has at least one car, traffic noise is inevitable and it keeps increasing. Poro(city) is imagined as a system that can be modified to the different site properties and later applied to many different locations. Since the approach for design fabrication is so adaptable based on basic measurements and environmental analysis, the idea can be performed easily.

As an example, the floating structure in between two buildings can be translated into a sculptural approach on the square. Design will change but the process remains the same. Depending on the noise level, aggregated units can be bigger or smaller, more or less dense, thicker, thinner etc.

The area in a developed industrial park may vary greatly from a wooded park nearby, as natural flora in parks absorbs light and heat in leaves that a building roof or parking lot just radiates back into the air. Advocates of solar energy argue that widespread use of solar collection can mitigate overheating of urban environments by absorbing sunlight and putting it to work instead of heating the foreign surface objects.

In addition, by creating a green oasis in the city center, we are bringing nature to the people. As already mentioned, because of the busy lifestyle, people often donâ&#x20AC;&#x2122;t have enough time to enjoy nature. With a small green structure in the center, people will have the opportunity to walk through nature for at least a small amount of time while going to work or walking back home.

Furthermore, the idea was to create something more than just a sound absorbing noise panel, something that could possibly have more benefits to the society than just the absorption of sound. The microclimate that comes with this idea can be a beneficial aspect of this performance.

A microclimate can offer an opportunity as a small growing region for crops that cannot thrive in the broader area; this concept is often used in permaculture practiced in northern temperate climates. Cities often raise the average temperature by zoning, and a sheltered position can reduce the severity of winter. In an urban area, both by overshadowing large areas and by channeling strong winds to ground level. Wind effects around tall buildings are assessed as part of a microclimate study.

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01 | Abstract 02 | Context - Worldwide Hearing Index 2017, Mimi Hearing Technologies GmbH - Changing the urban design of cities for health: The superblock model Natalie Mueller David Rojas-Rueda Haneen Khreis Marta Cirach David Andrés Joan Ballester Xavier Bartoll Carolyn Daher Anna Deluca Cynthia Echave Carles Milà Sandra Márquez Joan Palou - Publication from the Communications and the Urban Planning, Health and Environment Initiative at ISGlobal. Authors and collaborators (in alphabetical order): Ione Avila-Palencia, Xavier Basagaña, Aleix Cabrera, Glòria Carrasco, Ariadna Curto, Payam Dadvand, Carolyn Daher, Irene Eleta, Beatriz Fiestas, Maria Foraster, Mireia Gascon, Haneen Khreis, Èrica Martinez, Mark Nieuwenhuijsen, Natalie Mueller, David Rojas, Pau Rubio, Adelaida Sarukhan, Marta Solano, Jordi Sunyer, Raül Toran, Margarita Triguero and Wilma Zijlema. LAST UPDATE: APRIL 2018

03 | Research question - ACOUSTIC DIFFUSERS: THE GOOD, THE BAD AND THE, T J Cox, Salford University - What is soundscape ecology? An introduction and overview of an emerging new science, Bryan C. Pijanowski • Almo - Sound Materials – A Compendium of Sound Absorbing Materials for Architecture and Design

04 | State of the art - Guinness World Records article:Microsoft lab sets new record for the world’s quietest place written by By Rachel Swatman - article : Inside the world’s quietest room written by Jacopo Prisco - Visualization of the sound field around a Schroeder diffuser K.Fujiwara K. Nakai H.Torihara - Digital Fabrication Of Non-Standard Sound-Diffusing Panels Inthe Large Hall Of The Elbphilharmonie Author(S): Benjamin S. Koren And Tobias Müller Book Title: Fabricate 2017 - The University New South Wales, article called Helmoltz resonance by PhD student and luthier John McLennan - Acoustic black holes for flexural waves: A smart approach to vibration damping, Victor V. Krylov - Location of noise barrier and their effect on road safety, Author:Slavcheva – Semedzhieva

05 | Sound Characteristics - The Lean Optimization of Acoustic Diffusers: Design by Artificial Evolution & Time Domain Simulation

06 | Material system and Exploration

- A Compendium of Sound Absorbing Materials for Architecture and Design - Recent Trends in Porous Sound-Absorbing Materials Jorge P. Arenas, University Austral of Chile, Valdivia, Chile Malcolm J. Crocker, Auburn University, Auburn, Alabama - Kazragis, A., Gailius, A., and Jukneviciute, A., “Thermal and Acoustical Insulating Materials Containing Mineral and Polymeric Binders with Celluloses Fillers,” Material Sciences, Vol. 8, No. 2, pp. 193-195, 2002.

- Recent Trends in Porous Sound-Absorbing Materials - Schmid, M., and Schwertfeger, F., “Applications for Silica Aerogel Products,” Journal of Non-Crystalline Solids - FKA, Determination of Weight Elasticity of Fuel Economy for Conventional ICE Vehicles, Hybrid Vehicles and Fuel Cell Vehicles, Report 55510, Forschungsgesellschaft Kraftfahrwesen mbH, Aachen, 2007.

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- Nanocellulose-based foams and aerogels:processing, properties, and applications,Nathalie Lavoine and LennartBergstrom

07 | Design and Fabrication strategy

- Li, R.; Du, J.; Zheng, Y.; When, Y.; Zhang, X.; Yang,W.; Lue, A.; Zhang, L. Ultra-lightweight cellulose foam material: Preparation and properties. Cellulose 2017

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-Nechita, P.; Nastac, S. Foam-formed cellulose composite materials with potential applications in sound insulation. J. Compos. Mater. 2018.

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- Heinz, S.; Edmone, R. Composite corkplate and method for the production thereof. European Patent EP1048424, published November 02, 2000.

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- Porous materials for sound absorption by Leitao Cao, Qiuxia Fu Yang Si, Bin Ding, Jianyong Yu - Nedderman, 1992, 1; Duran, 2000, vii - Dierichs, K., Menges, A.: 2010, Material Computation in Architectural Aggregate Systems, in Life In:Formation: On Responsive Information and Variations in Architecture, Proceedings of the 30th Conference of the Association For Computer Aided - Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018 - Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018 Image Source: gramazio kohler research, ETH zürich - Design Computation Lab, UCL, RC4 -Mickeymatter, tutors: Gilles Retsin, Manuel Jiménez García with Vicente Soler students: Panagiota Spyropoulou, Hyein Lee, Pooja Gosavi, Pratiksha Renake

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08 | Unit design process

-Materials Science & Engineering C, Hydroxyapatite bioceramic with large porosity, M. Mbarki, P. Sharrock, M. Fiallo, H.ElFeki

-Granular construction, Karola Dierichs and Achim Menges, Institute of Computational Design, Stuttgart, Germany, 2018

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-Optimization Modeling with Spreadsheets,By Kenneth R. Baker

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09 | Feometry design process

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10 | Case study 11 | Conclusion - Pisello, Anna Laura; Saliari, Maria; Vasilakopoulou, Konstantina; Hadad, Shamila; Santamouris, Mattheos (2018). “Facing the urban overheating: Recent developments. Mitigation potential and sensitivity of the main technologies”.

- Nature spot webpage -Cartilage Lichen - Ramalina farinacea - The Secret Life Of Lichens, In Exhibits by Cambridge Butterfly Concervatort, November 24, 2016 - Spending at least 120 minutes a week in nature is associated with good health and wellbeing Mathew P. White, Ian Alcock,James Grellier,Benedict W. Wheeler, Terry Hartig,Sara L. Warber, Angie Bone, Michael H. Depledge & Lora E. Fleming - Natural Rubber - From A Gooey Sap To A Usable Material - Bob Jackson - Natural Rubber Adhesives - K.F.Gazeley, W.C. WakeRubber - Chris Woodford -Natural Rubber: Structure and Function-By D.J. Miller - Valuable source - Mechanical and Corrosion-Resistant Properties of Plastics and Elastomers

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PORO(CITY) // Digital Matter Studio is a project of IaaC, Institute for Advanced Architecture of Catalonia developed in the Master in Advanced Architecture 2019/20 Students:Matin Darabi, Hanna Lepperød, Ilaena Mariam Napier, Ines Cavar Faculty: Areti Markopoulou, Raimund Krenmueller, David Andres Leon, Nikol Kirova.