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Sound Design As important as climate control and adequate lighting, acoustical enhancements help create “people friendly” environments

All occupiable structures – from single-family dwellings to apartment complexes, from office buildings to lecture halls – should be “people friendly” environments. This includes climate control, adequate lighting, and appropriate acoustic properties. During the preliminary design phase, clients should be informed of the importance of the acoustic environment. Otherwise, clients may not consider acoustics until problems in the final structure appear. Since hearing is one of our senses and oral communication is essent, acoustic properties of a space are essential to human interaction. Noise should not be annoying and at a low enough level to not interfere with speech. Acoustic privacy should prevent outside noise or speech from entering into the space and the noise within from escaping. Then reverberation should be low enough to ensure intelligible speech. What are the technologies required to control the acoustic environment? There are noise control and room acoustics. In noise control, the concern is the noise source and the paths by which noise affects the occupied space. These include walls, floors, ceilings, windows, air ducts, and vibrations. Vibrations of the structure by machinery or plumbing are radiated as noise into the room. The best solutions are to use quiet machinery and vibration isolation. Room acoustics provide methods for designing an acoustic environment appropriate to the intended use of the space. If the direct sound and no reflections are heard, the space is considered “dead.” People generally prefer a “live” space in which they can hear the reflection of their voice delayed a few milliseconds. If multiple reflection of a sound lasts hundreds of milliseconds, the space is too “live” and intelligible speech is impaired. Optimal reverberation times range from 300 milliseconds for small rooms and 1.4 seconds for large rooms such as auditoriums. Reverberation times are controlled by the amount of acoustic absorption on the inside surfaces of the room. Reverberation time is proportional to the volume divided by the absorbing area. The absorption coefficient may vary from


t e x a s

a r c h i t e c t

Thaddeus Leopoulos

By Elmer L. Hixson, PhD

Florida-based Arquitectonica collaborated with Gensler on the design of the Hilton Americas-Houston to include strategies for enhanced acoustical absorption and sound isolation. The techniques serve to block noise from outside and retain interior sound within each space.

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Texas Architect March/April 2006: Preservation