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H O W

The Ear

H U M A N S

P E R C E I V E

S O U N D

AN ORIGINAL SCIENCE CENTER EXHIBITION e


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H O W

H U M A N S

P E R C E I V E

S O U N D

AN ORIGINAl SCIENCE CENTER EXHIBITION

Marquis Love

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Copyright © 2013 by Bill Shakespeare All rights reserved. No part of this publication may be reproduced, distributed, or transmitted in any form or by any means, including photocopying, recording, or other electronic or mechanical methods, without the prior written permission of the publisher, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law. For permission requests, write to the publisher, addressed “Attention: Permissions Coordinator,” at the address below. Imaginary Press 1233 Pennsylvania Avenue San Francisco, CA 94909 www.imaginarypress.com Ordering Information: Quantity sales. Special discounts are available on quantity purchases by corporations, associations, and others. For details, contact the publisher at the address above. Orders by U.S. trade bookstores and wholesalers. Please contact Big Distribution: Tel: (800) 800-8000; Fax: (800) 800-8001 or visit www.bigbooks.com. Printed in the United States of America Publisher’s Cataloging-in-Publication data Love, Marquis. A title of a book : a subtitle of the same book / Marquis Love p. cm. ISBN 978-0-9000000-0-0 First Edition 14 13 12 11 10 / 10 9 8 7 6 5 4 3 2 1


We dedicate this book to all of you with our love, appreciation, and thanks for allowing us to be a part of your lives.

Enjoy!

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The Contents Withiďż˝

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Introduction/3. how sound works/4. what we hear /6. sections OF THE EAR/8. inner structure/10. FUN FACTS/12. I do not own the rights to some of the articles reproduced within. “How we hear” is an article originally published on how stuff works website, the original author is tom harris. The article “Mammalian ear” was taken from an excerpt from wikipedia.com. All rights reserved to its original authors

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Introductio�

Did you hear something? Maybe the sound you heard was as quiet as your cat licking her paws. Or maybe it was loud, like a siren going by. Sounds are everywhere, and you have two cool parts on your body that let you hear them all: your ears! Your ears are in charge of collecting sounds, processing them, and sending sound signals to your brain. And that’s not all — your ears also help you keep your balance. So if you bend over to pick up your cat, you won’t fall down — or even worse — fall on your cat. Meow!

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//how sound works

How we hear

how stuff works/ by tom harris Often the entire organ is considered the ear, though it may also be considered just the visible portion. In most mammals, the visible ear is a flap of tissue that is also called the pinna (or auricle in humans) and is the first of many steps in hearing. Vertebrates have a pair of ears placed somewhat symmetrically on opposite sides of the head. This arrangement aids in the ability to localize sound sources.

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How We Hear cont’d BY TOM HARRIS

Your ears are extraordinary organs. They pick up all the sounds around you and then translate this information into a form your brain can understand. One of the most remarkable things about this process is that it is completely mechanical. Your sense of smell, taste and vision all involve chemical reactions, but your hearing system is based solely on movement. In this article, we’ll look at the mechanical systems that make hearing possible. We’ll trace the path of a sound, from its original source all the way to your brain, to see how all the parts of the ear work together. When you understand everything they do, it’s clear that your ears are one of the most incredible parts of your body!

To understand how your ears hear sound, you first need to understand just what sound is. An object produces sound when it vibrates in matter. This could be a solid, such as earth; a liquid, such as water; or a gas, such as air. Most of the time, we hear sounds traveling through the air in our atmosphere. When something vibrates in the atmosphere, it moves the air particles around it. Those air particles in turn move the air particles around them, carrying the pulse of the vibration through the air. To see how this works, let’s look at a simple vibrating object: a bell. When you hit a bell, the metal vibrates -- flexes in and out. When it flexes out on one side, it pushes on the surrounding air particles on that side. These air particles then collide with particles in front of them, and so on. 5


//what we hear

NEW PRODUCT

SLALOM/FREERIDE NORTHSAILS 7.5

psychoacoustics

WHAT WE PERCEIVE OF SOUND

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//sections of the ear MAMMALIAN EAR

THE SENSE OF SOUND The outer part of the ear collects sound. That sound pressure is amplified through the middle portion of the ear and, in land animals, passed from the medium of air into a liquid medium. The change from air to liquid occurs because air surrounds the head and is contained in the ear canal and middle ear, but not in the inner ear.

The outer ear is the most external portion of the ear. The outer ear includes the pinna (also called auricle), the ear canal, and the very most superficial layer of the ear drum (also called the tympanic membrane).

The inner ear is hollow, embedded in the temporal bone, the densest bone of the body. The hollow channels of the inner ear are filled with liquid, and contain a sensory epithelium that is studded with hair cells. The microscopic “hairs� of these cells are structural protein filaments that project out into the fluid.

The middle ear, an air-filled cavity behind the ear drum (tympanic membrane), includes the three ear bones or ossicles: the malleus (or hammer), incus (or anvil), and stapes (or stirrup). The opening of the Eustachian tube is also within the middle ear.

The hair cells are mechanoreceptors that release a chemical neurotransmitter when stimulated. Sound waves moving through fluid push the filaments; if the filaments bend over enough it causes the hair cells to fire. In this way sound waves are transformed into nerve impulses.The nerve impulses travel from the left and right ears through the eighth cranial nerve to both sides of the brain stem and up to the portion of the cerebral cortex dedicated to sound.

The inner ear includes both the organ of hearing (the cochlea) and a sense organ that is attuned to the effects of both gravity and motion (labyrinth or vestibular apparatus). The balance portion of the inner ear consists of three semicircular canals and the vestibule.

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Structure of the ear The parts inside of your ear that help you hear are tiny! Even though noises can seem really loud, they are detected by very small parts: • •

• OUTER EAR

The three bones in your ear are the smallest bones in your body, and all three could fit together on a penny. The inner ear is about the size of a pencil eraser, but it contains more than 20,000 hairs. If those hairs were the size of a pencil, you could create a stack of them 433 feet tall. About the same height as a 43 story skyscraper. The smallest muscle in the body is the stapedius, located in the middle ear. It is only 1/20th of an MIDDLEbone EAR in the body, the stapes or stirrup bone. inch long and controls the smallest

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//inner structure

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The process of hearing HOW HUMANS HEAR SOUND

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A sound wave is a chain of vibrating air molecules. When objects vibrate, their movement causes the air molecules around them to vibrate too. The vibrations are channeled into your ear canal, where they strike your eardrum.

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The eardrum vibrates and sets off a chain reaction, vibrating the hammer, anvil, and stirrup bones behind it.

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This moves fluid in a tube called the cochlea, and tiny hairs called cilia move, sending electrical messages to your brain via the auditory nerve.

Cool!

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//fun facts Did you know?

The malleus, incus and stapes (otherwise known as the hammer, anvil and stirrup) are the smallest bones in the human body and are full size at birth. All three together could fit on a penny.

The really cool stuff

The whole area of the middle ear is no bigger than an M&M.

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The cochlea (inner ear) is about the size of a number two pencil eraser. The ear never stops working, even when people are asleep. The ear continues to hear sounds, but the brain shuts them out. Ears are self-cleaning. Pores in the ear canal produce cerumen, or ear wax, and tiny hairs, called cilia, push the wax out of the ear. At birth, the human ear can hear sounds as low as 20 Hertz (lower than the lowest note on a piano) and as high as 20,000 (Hertz) (higher than the highest note on a piccolo)


Thanks, for reading! Now you have great knowledge about the human ear!

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The Human Ear  

Maybe the sound you heard was as quiet as your cat licking her paws. Or maybe it was loud, like a siren going by. Sounds are everywhere, and...

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