Auditory Science Facts

By Charles Pidgeon and Yash Gupta

The book was designed to be a textbook or supplementary material for any high school or college course involved with Hearing and Balance. The format of the book is questions followed by answers. Students can use the book for self-teaching with the answers containing follow up references. Many of the authors and Illustrators are high-school stude

• Language: English
• Publisher: Dr. Charles Pidgeon Books
• Release date: Sep 3, 2021
• ISBN: 9781641336499

Charles Pidgeon

Matthew Trotter joined the Neuroscience Sensory founded by Dr. Charles Pidgeon as a Freshman at Princeton. Matthew graduated in 2021 and is currently attending Medical School. At Princeton, Mr. Trotter majored in Neuroscience. He meticulously went studied the modern literature of taste from the perspective of several scientific disciplines: anatomy, physiology, genetics, biology, etc.

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Copyright © 2021 by Yash Gupta and Dr. Charles Pidgeon.

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 author, except in the case of brief quotations embodied in critical reviews and certain other noncommercial uses permitted by copyright law.

ISBN 978-1-64133-649-9 (ebook)

Library of Congress Control Number : 2021911445

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Dedication

Brian Charles Pidgeon, My Son

Jiaming Yen, My Student

Table of Contents

Author’s Note

Preface

Introduction

Questions

Part I: The Auditory Pathway

1. The Ear

2. Brainstem Structures

3. Cortical Circuitry

Part II: Language, Music and Cortical Circuitry

1. Sound

2. Language

3. Music

Part III: Development

1. Fetal Development

2. Infants and Children

3. Aging

Part IV: Diseases

Part V: Evolution

Answers

The Auditory Pathway

1 The Ear

2 Brainstem Structures

3 Cortical Circuitry

Sound, Language and Music

1 Sound

2 Language

3 Music

Development

1 Fetal Development

2 Infants and Children

3 Aging

Diseases

Evolution

Glossary

Index

Author’s Note

If a tree falls in the forest and no one hears it, does it make a sound?

George Berkeley (1685-1753) was a philosopher, writer, and bishop who made a proposition about sensation to prove the existence of God. His intellectual puzzle, phrased in the question above, motivated individuals to believe in God simply because there was no other explanation at that time. Berkeley argued that the reality of the external world arises from perception. So, if a tree falls in a forest, but no one hears it or sees it, did it actually fall? If perception creates reality, then why doesn’t the tree simply disappear when no one looks at it? To answer this question, Berkeley contended that there must be an omnipresent god who is viewing everything in order for everything to exist. He believed the reason why the tree still fell without anyone looking at it was that God was looking at it the whole time.

Regardless of Berkeley’s understanding, hearing is an outcome of an evolutionary process that resulted in the ability of people to detect, process, and interpret sound. Berkeley’s simplistic explanation of the puzzle (that God heard it) gave people a fake proof of God’s existence. This is because one of Berkeley’s axioms was that reality comes only from perception. Thus, he reached an unreasonable conclusion. In reality, this question cannot prove nor deny the existence of God. By the same token, perceived phenomena are not always reality. For example, many musicians are able to perceive music in their minds without hallucinating through a process known as musical imagery. This perception lacking a stimulus is not rooted in reality, rather it is a product of the mind. This is also true of auditory and optical illusions.

Mr. Berkeley tried to use a physical observable to prove the existence of a God, but this line of reasoning is deeply flawed. The argument, however, was successful, and people who were once skeptical of God considered changing their belief system and accepting Mr. Berkeley’s proposal. Mr. Berkeley also promoted the concept that all emotions, perceptions, and interpretations of God occur because it is God himself who turns them into ideas. If Mr. Berkeley was able to study the current neuroscience known today, he would understand that all perceptions of reality are actually just constructs of the human brain expressed in each individual mind.

When scientists cannot observe the results of a prediction, they denote it as a theory. While theories may not be immediately tested, some scientists consider them true as an assumption to build upon. However, no matter how compelling a theory may be, it may still be incorrect. Over the thousands of years that people have speculated about the existence of God, no one has given any concrete evidence to support this theory, so the concept of God remains an unproven belief.

As long as there is a medium (such as air), a tree falling will always create a pressure wave that is sound energy. But the personal interpretation of sound, which is a construct of the individual’s brain, is necessary for hearing. Given today’s knowledge base, the thinking that Berkeley’s puzzle based on sound as a validation for the existence of God should be evaluated as a circular argument: (i) the true sound produced, but not heard, (ii) God hears everything, (iii) a true sound was heard →(i)→(ii)→(iii)… The conclusion that god exists is buried in the circle. The difference between physical observables (i.e. sound) and words (i.e. God) is that physical observables exist with or without words. When people did not inhabit the earth there were a lot of different sounds (with frequencies and intensities) but there were no people around who needed a concept of God and the word itself did not even exist.

After reading this book, individuals should be able to have a highly-satisfying knowledge which they could apply to Berkeley’s puzzle. Further, the reader will hopefully be able to use rational thinking and plausible assumptions to explain auditory phenomena.

The author believes that proving the existence of any spiritual entity (which is, by definition, a non physical observable) using sound is not logical or rational. Those who require the emotional satisfaction of explaining Berkeley’s puzzle may think or say, Sometimes you just have to believe. Others who do not feel the necessity of explaining everything they don’t understand, perhaps scientists and many non-scientists with like minds, may not have the emotional need to just believe. Per usual, it is a personal choice. It is acceptable for people to want to feel comfortable and if believing in God is the way to do it, then fine.

However, it is a classical mistake in science to explain something unknown with another unknown, and a recent example of this was discussed in neuroscience. Ramachandran VS & Hubbard EM (2001). [Synaesthesia: A window into perception, thought and language (PDF). Journal of Consciousness Studies. 8 (12): 3–34 (2001).] Explaining the existence of one mystery (i.e. God) with another mystery (i.e. sound properties), is inappropriate, but forgivable, because auditory science didn’t exist during Berkeley’s lifetime. We, therefore, suggest that the ineffable God may catalyze circular arguments with scientists that should be avoided, stopped, or at least minimized. Auditory Perception is about facts and is not written for readers to use during intellectual conversations, debates, and paradoxes regarding any religious belief.

Auditory Science Facts: Auditory and Balance Perception is the second book in a series devoted to understanding each primary sensory system. The first book, Vision Facts: Questions about the Human Eye, provides supplemental educational material on the topic of visual perception. The full series will provide a learning experience, through questions and answers, about different sensory systems humans use to generate a perception of the world that they live in. A glossary of terms and an index are included for easy reference and learning. This book is not concerned with proposals, arguments, or belief systems people may engage in with each other based on the sensory systems available for all of us to engage in the world.

Dr. Charles Pidgeon

Preface

Hearing Facts addresses the summarized concepts from the introduction in great detail. First, the anatomy of the ear and the auditory pathway are described. Different types of hair cells are discussed, along with an explanation of how rapid depolarization and hyperpolarization are achieved. Topics also explored include language and music, hearing development and progression, and hearing diseases. Finally, the text discusses how hearing arose through evolution.

Presented in a question-and-answer format, Hearing Facts is an excellent resource for all who are interested in auditory perception. The author, Dr. Charles Pidgeon, is a former professor at Purdue University. Hearing Facts is the second book of a series aimed at providing an extensive understanding of the various senses that humans possess to perceive the world around them. Aiding Dr. Pidgeon is a group of students interested in learning more about the processes that allow humans to understand the world around them.

We hope that this text will provide an informative and enjoyable way to learn more about the auditory system.

Introduction

Whether it be a pigeon chirping or the bass line from your favorite album, the sound is all around us. Breaking it down to the simplest terms, the sound is just pressure differences in the air. It is formed from compressions and rarefactions of air that the ear can pick up. The hearing process first begins in the outer ear, when the incoming sound wave hits the visible portion of the ear, called the pinna. The pinna funnels the sound through the ear canal, also known as the external auditory meatus.

By this point, the sound has traveled through the outer ear and is about to enter the middle ear. As the sound wave hits the tympanic membrane (commonly called the eardrum), the membrane vibrates, which in turn moves three adjacent bones known as the ossicles. These bones called the malleus, incus, and stapes, are housed in the middle ear and connect the tympanic membrane to the cochlea. Their function is to amplify and propagate the sound stimulus across the middle ear.

The movement of these bones pushes on the oval window of the cochlea, a snail-shell like structure located in the inner ear essential to the detection of sound. The cochlea is filled with two fluids called perilymph and endolymph, and transduces vibrational energy into action potentials. As the oval window is pushed inwards by the stapes (the last of the aforementioned ossicles), the perilymph fluid also moves, indirectly pushing on the basilar membrane. On top of the basilar membrane is the organ of Corti, a structure containing hair cells responsible for converting sound into electrical signals. The movement of the basilar membrane causes mechanically gated ion channels located on the stereocilia of these hair cells to open, leading to hair cell depolarization and the creation of an electrical signal.

The signal is passed on through the vestibulocochlear nerve, also known as cranial nerve VIII. This nerve connects the cochlea with various regions in the brainstem that act as relay stations. The signal travels up the brainstem, starting at the cochlear nucleus, where neurons first come into contact in the brainstem. and going through a variety of other structures such as the trapezoid body, the superior olivary complex, the inferior colliculus, and the medial geniculate nucleus in the thalamus.

From the thalamus, the auditory radiation brings information to the primary auditory cortex, the site where most auditory processing is done. This cortical region is a part of the temporal lobe, and is involved in the actual decoding of the neural messages from the cochlea. Another important cortical region for hearing includes the auditory association areas, which integrate various other sense information with auditory information to better interact with the world. There is also Wernicke’s area, consisting of part of the temporal lobe, which is important in understanding speech. Together, these regions, along with the many other cortical regions, truly shape the reaction and understanding of a sound stimulus, which is why many say that you do not hear with your ears, instead, you hear with your brain.

To summarize, the incoming sound wave enters the ear and is converted into vibrational energy when it hits the tympanic membrane, resulting in the movement of the ossicles. The movement of the ossicles