ound can mean different things to different people depending on the situation For instance a train whistle might let an excited traveler at a railway sta tion know he or she is about to leave on a long awaited trip For someone walking near train tracks however that same whistle serves as a warning that an engine is coming and the person needs to get out of its path Likewise a dog barking at night might make the pooch's owner feel safe from burglars but may simply annoy neighbors trying to sleep Regardless of the situation or interpre tation all sounds have things in common mainly how they are produced and how they are processed by those who hear them This book reveals the physics behind sound i creation and details the various properties of sound It also reveals that the fleshy bits of the human ear visible on either side of a person's head are just the tip of the iceberg when it comes to the ear’s form and func tion Readers are taken on a virtual journey through the human ear for an explanation of how sound is heard Also discussed is the field of acoustics t
INTRODUCTION Sound is produced in waves caused by vibrations The movement of the vibration pushes and pulls air molecules which crowd together and form invisible ripples in the air These ripples called compression waves travel from the source of the vibration in all directions until they reach a pair of ears which translate the vibrations into sound Strength and frequency how quickly one complete vibration occurs each affect how sound is heard How strong a vibration is determines whether a sound is loud or soft the stronger it is the louder Frequency influences pitch which is how high or low a sound is Sometimes a solid object blocks the path of sound waves traveling through the air Sound is easily reflected from flat surfaces meaning that the sound waves reflect off of the object and turn back toward the source Reflection explains why there is an echo when a person shouts into a canyon that has flat smooth walls Reflecting off of curved objects restricts the paths that waves can take thereby focusing sound as it travels from the
SOUND The curved shape of part of the outer human car known as the external auditory meatus or ear canal helps focus sound as it is received Sound waves journey down the ear canal to a membrane called the ear drum Waves striking the eardrum cause it to vibrate From there sound waves travel to the middle ear where they are passed along a series of three small bones called ossicles and strike another membrane called the round window Finally sound moves into the inner ear to the shell like cochlea which houses the organ of Corti Covered in nerve endings that look like tiny hairs the organ of Corti sends electrical impulses to the brain where sound is identified There are many kinds of sounds and various ways to interpret those sounds But as this book explains the physics of sound are pretty straightforward as well as quite interesting 8
