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