HEARING

Audition

What is Audition? Hearing

What sounds do we hear the best?

Sounds with the frequencies in the range corresponding to the human voice.

How Sounds Travel to the Ear A sound Stimulus Energy Molecules of Air bump into the next

molecules waves of compressed & expanded air

Ears detect the air pressure change The vibrations are felt Ears transform the vibrating air

nerve impulses

Sound Waves

Amplitude Strength of the sound waves Loudness

Frequency The number of wavelength that pass a point in

a given time which determines the pitch Pitch

A tone’s experienced high or lowness Decibels

How sounds are measured The absolute threshold for hearing is arbitrarily

Structure of the Ear

The ear is divided into the outer, middle & inner ear.

Outer Ear

Auditory Canal #7 Channel that

sounds Waves first pass

through

Eardrum #8 A tight membrane that vibrates with the waves

Middle Ear

Bones of the middle ear = the Hammer #1, Anvil #2, Stirrup #3 which vibrate with the eardrum.

Semicircular Canals #4

Inner Ear

Oval window = where the stirrup connects to the cochlea. #9

Cochlea = a coiled, bony, fluid-filled tube in the inner ear through which sound waves trigger nerve impulses. #6

Perceiving Loudness

Basilar membrane’s hair cells

Cochlea and Loud Sounds

Auditory nerve = nerve which sends the auditory message to the brain via the thalamus. #5

Eustachian Tube #11

The eustachian tube connects the middle ear to the throat.

Its purpose is to equalize middle ear pressure with environmental pressure. When your ear "pops" on a high-speed elevator or in an airplane, the reason is that the eustachian tube has opened and equalized pressure.

Neural Impulse to the Brain

Place Theory

The theory that links the pitch we hear with the place where the cochlea’s membrane is stimulated.

Frequency Theory

The theory that the rate of nerve impulses traveling up the auditory nerve matches the frequency of a tone, thus enabling us to sense its pitch.

Hearing Loss

Conduction Hearing LossHearing loss caused by damage to the mechanical system that conducts sound waves to the cochlea.Problems with the eardrum or three bones of the middle ear.

Sensorineural Hearing LossHearing loss caused by damage to the cochlea’s receptor cells or to the auditory nerves; also called nerve deafness.