lecture 3 - exam 1

Question 1

cone of light for right ear

Answer 1

on the right side

Question 2

cone of light for left ear

Answer 2

on the left side

Question 3

purposes of the pinna

Answer 3

collects sound waves & directs them toward the ear canal

amplifies sound - esp. high freqs

vertical localization

Question 4

what shape is the ear canal

Answer 4

s-shaped

2 turns

Question 5

how long is the avg adult ear canal

Answer 5

~2.5cm

Question 6

parts of the ear canal

Answer 6

membranous = outer 1/3

osseous = inner 2/3

Question 7

purposes of ear canal

Answer 7

protects ear from foreign bodies, humidity, temp changes, etc

ear canal is a tube
resonates
natural freqs = key freqs for speech

Question 8

transfer functions

Answer 8

describe how a system affects some signal

typically show either input/output ratios by freq or gain by freq

Question 9

what has transfer functions

Answer 9

head

outer ear

middle ear

cochlea

hearing aids & cochlear implants

Question 10

purpose of the TM/ear drum

Answer 10

transduce air pressure waves into mechanical vibrations in the ear

Question 11

middle ear bones

Answer 11

malleus -thick

incus - middle

stapes - horseshoe

Question 12

malleus

Answer 12

manubrium embedded in the TM

Question 13

incus

Answer 13

connects malleus to stapes

Question 14

stapes

Answer 14

footplate of the stapes pushes into the entry of the cochlea - the oval window

Question 15

purpose of the ossicles

Answer 15

impedance matching

protection from loud sounds

tuning

Question 16

impedance mismatch

Answer 16

when 2 mediums have different impedances (mass & stiffness)

air & fluid have different impedances -most acoustic energy from the air will be reflected by fluid

pressure must be increased to transduce air pressure into fluid waves in the cochlea

w/out middle - 98% of energy will be reflected back

Question 17

2 mechanisms of impedance matching

Answer 17

area ratio

lever action

Question 18

area ratio

Answer 18

area of oval window is 20x smaller than the TM

for the same force, the pressure generated at the oval window is greater

Question 19

lever action

Answer 19

the malleus & incus act as a lever system

output force > input force

malleus is long compared to the incus & fulcrum is close to stapes

Question 20

middle ear muscles

Answer 20

tensor tympani

stapedius

Question 21

tensor tympani

Answer 21

pulls inward on malleus & tenses the ear drum

increases stiffness & therefore increases impedance

Question 22

stapedius

Answer 22

pulls so stapes rotates out of the oval window & increases the stiffness of the ossicular chain

increases impedance

Question 23

how do middle ear muscles contract

Answer 23

contract involuntarily to loud, low freq stimuli

Question 24

tensor tympani also activated by

Answer 24

swallowing

pharynx preparing for speech production

Question 25

stapedius also activated by

Answer 25

pharynx preparing for speech production

Question 26

purpose of middle ear muscles

Answer 26

reducing transmission of low freqs during chewing or speech improve speech in noise perception

Question 27

eustachian tube

Answer 27

connects middle ear to nasopharynx opens & closes to equalize pressure & provide ventilation & drainage between ear & throat