Chapter 4: Audition
1 1. Sound
Sound is just the motion of molecules transmitted via compressed airwaves. 1. Sound
• Sound waves are pressure changes in a
• Physical properties: amplitude, frequency
• Perceptual properties: loudness, pitch,
The higher the Frequency the higher the pitch.
Timbre- large complex or simple waves. How we perceive different instruments
playing the same not ie C note on guitar vs piano.
Ave human can hear 20-20 000Hz Muscles vibrate at 25hz- can hear muscles
work 2. The ear
a) Outer ear
• We can hear a range from 20 to 20,000
a) Middle ear (3 bones)
• Density mismatch problem
a) Inner ear (3 scalae, 2 windows, & an
4 The Ear
KNOW ALL THE PARTS OF THE EAR/PINNA
Density mismatch from air- water. Lose a lot of energy because cochlea filled
with fluid. Difference in SA and Lever principle overcomes this.
SA 17:1 ratio focuses energy on a single point- boosting hearing/amplifies 17 x
Lever Principle:The hammer anvil and stirrup swing and x1.3 amplifies (=22 x)
(they are also the 3 smallest bones in the human body)
Fxn of round window to provide pressure relief Good when hearing under water The Ear
Open up BASILAR, looks like flipper. Where Transduction takes place (change
in size b//w basilar and cochlea rolled and flat) 5x more outer cilia than inner, yet
majority info comes from inner cilia. The Ear
Temp and Basil membranes push against the hairs, the inner hair cells send
action potential while outer help amplify signal/raise the roof 3. Coding frequency
Phase locking & Place coding
•eurons fire at 1,000 /sec.
•ery low freq. = phase locking
•edium freq. = phase locking & place coding
•ery high freq. = place coding.
Phase looking- 500htz tone= 500 neurons ect..
Anything above 20000 can't be heard. Solved by Place coding- different places
along basilar membrane deflect and measure frequencies):
Low freq= phase locking
Interm= place coding+ phase locking
High freq= place coding
How does relate to specificity theory? Relates to call as each location require
diff neurons Coding frequency
9 Auditory cortex
Cochlea 10 4. Localizing sound