Chapter 6 Part II – HEARING
I.
HEARING/AUDITION
A.
Just like light waves from the electromagnetic spectrum, we detect sound from SOUNDWAVES in
the air around us.
1. Sound waves travel faster through SOLIDS and slower through AIR.
2. FREQUENCY:
Distance from peak to peak.
Determines PITCH (Hertz)
B.
Structure of the EAR
1.
Outer Ear (humming activity) - Bottom
a.
Pinna/Auricle *Chanel Activity
b.
Ear Drum
c.
Ear Canal
2.
3.
Middle Ear
a.
Hammer, Anvil, Stirrup-
b.
Cochlea: Snail-shaped inner ear mechanism. Lined with neural receptors for hearing.
c.
Basilar Membrane: Lining of the cochlea containing receptor neurons.
d.
Hair Cells –
Found on basilar membrane
These are the receptor cells for hearing
They are surrounded by fluid and bend when fluid vibrates
Auditory Nerve (top) – Made of axons of the hair cells. Sent signal to temporal lobes.
How do we hear?
1.
PLACE THEORY:
2.
Malleus, Incus, Stapes
Inner Ear
a.
Oval Window: Opening to the inner ear. Similar to ear drum – vibrating membrane
*
C.
AMPLITUDE:
Distance from top to bottom
Determines VOLUME (Decibels)
*Damage at 80 Decibels
*Definite damage at pain threshold/ringing
Pitch is determined by the PLACE on the BASILAR MEMBRANE
where the sound waves stimulate hair cells.
a.
This is proof for how we hear: HIGH PITCH
b.
This is NOT proof for how we hear:
FREQUENCY THEORY:
a.
Medium/Low
Our brain reads PITCH based on the FREQUENCY/SPEED
of the neural signals coming in from the auditory nerve.
This is proof for how we hear: Medium/Low and some high pitches
b.
This is still NOT proof for how we hear:
Extremely high pitch
3.
VOLLEY PRINCIPLE: Neural signals DO NOT all fire at once. They ALTERNATE in
firing. In other words, they VOLLEY back and forth. When
certain neurons fire together, it creates a GREATER
frequency, explaining HIGHEST pitch sounds.
4.
Sound waves AND Bone Conduction:
a.
Why is pitch different on a video recording?
You always hear – air AND bone conduction
Others/DVD always hear – AIR conduction only
b.
5.
Plug your ears and talk. This is an example of BONE CONDUCTION.
How do we locate sounds in space?
*Clapping Activity
Your ears are separated for one to pick up the sound slightly faster than the other.
You instinctively locate the sound as directed by the ear that picks up the signal first.
D.
Hearing Damage
1. Decibel Chart (attached)
2. Conduction Deafness:
a.
Treatment:
3. Nerve Deafness:
a.
Treatment:
4. Tinnitus:
a.
Treatment:
Damage to outer or middle ear. (sound cannot be CONDUCTED in)
*Wax build-up/Cold/Ear Infection/Ear drum bursts
Get well/clean ears/hearing aids to amplify sound
Lack neurons or functioning neurons (hair cells)
*Auditory nerve damage
*Cochlear damage
*Genetics/Environment/Aging
Hearing Aids
Cochlear Implants
Ringing in the ears
*Genetics/Aging
*Noise over exposure
*Virus
*Water
Hearing Aids/Maskers
5. Controversies surrounding deafness?
Deaf Culture – language/lifestyle/community
vs.
Hearing Culture – language/lifestyle/community
What do you do for a deaf child/individual who has deaf parents yet could successfully hear with an
implant?
http://www.youtube.com/watch?v=PvvDf4RUtc8