Ear Lab Report

Aim:

The aim of this project is to determine the ear's ability to allow us to perceive the pitch of sounds by detection of the wave's frequencies, the loudness of sound by detection of the wave's amplitude and the timbre of the sound by the detection of the various frequencies that make up a complex sound wave.

Introduction:

Understanding how humans hear is a complex subject involving the fields of physiology, psychology and acoustics.

The ear consists of three basic parts - the outer ear, the middle ear, and the inner ear. Each part of the ear serves a specific purpose in the task of detecting and interpreting sound. The outer ear serves to collect and channel sound to the middle ear. The middle ear serves to transform the energy of a sound

The earflap provides protection for the middle ear in order to prevent damage to the eardrum. The outer ear also channels sound waves that reach the ear through the ear canal to the eardrum of the middle ear. Because of the length of the ear canal, it is capable of amplifying sounds with frequencies of approximately 3000 Hz. As sound travels through the outer ear, the sound is still in the form of a pressure wave, with an alternating pattern of high and low pressure regions. It is not until the sound reaches the eardrum at the interface of the outer and the middle ear that the energy of the mechanical wave becomes converted into vibrations of the inner bone structure of the ear.

The Middle Ear

The middle ear, also known as the tympanic cavity, is an air-filled space between the Ear Canal and the Eustachian Tube and the Cochlea. The middle ear has two major functions, it not only protects the Inner Ear but also transforms the quivering of the air coming from the outer ear into vibrations that the inner ear can analyze. The transformation and the amplification of the air quivering, is done by the help of the three ossicles found in the tympanic cavity.

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It terminates in the eardrum which is technically known as the tympanic membrane. The purpose of the external ear is to transmit sounds from the outside world into the more internal parts of the auditory system. While one can simply think of the pinna and ear canal as a simple funnel for collecting sounds, in reality they perform some important functions. The pinna has various ridges and folds that act to reflect and absorb certain frequency components of the sound wave . Because the pinna is not circularly symmetric, sounds which come from different directions will have slightly different spectral characteristics. (This means that certain frequencies will be slightly louder or softer depending on the direction they enter the ear.) As a result, sounds which come from above our heads seem slightly different than sounds coming from below. This allows us to localize (pinpoint the direction of) a sound source. We therefore immediately look up when someone calls us from an upper story