auditory perception - exam 2

Question 1

sound transformation up the auditory pathway

Answer 1

sound waves begin as vibrations in the air

enter ear canal

move through various stages

converted to neural signals in the brain

Question 2

air bone fluid

Answer 2

air = sound waves

bone = ossicular vibrations

fluid = basilar membrane waves

Question 3

outer ear

Answer 3

filters the sound

air

Question 4

ear canal resonance

Answer 4

the resonance of the ear canal = the resonance of the vocal tract

amplifies the resonant frequencies of speech

Question 5

middle ear

Answer 5

converts air vibrations into mechanical vibrations using eardrum & ossicles

Question 6

inner ear (cochlea)

Answer 6

translates mechanical vibrations into electrical signals through hair cells

Question 7

auditory nerve

Answer 7

carries electrical signals to the brain

interpreted as sound

Question 8

limits of the auditory system

Answer 8

upper & lower bounds of hearing freqs (20-20,000 Hz)

neural saturation

temporal resolution - VOT

Question 9

neural saturation

Answer 9

where high sound intensities cause neurons to max out

restricting dynamic range & clarity in hearing

sounds that follow other sounds don’t get as big of a neural response - neurons need time to rest

Question 10

threshold of audibility

Answer 10

softest sound that can be heard

varies w/ freq

“0 loudness”

Question 11

equal loudness curve

Answer 11

different freqs need varying sound pressures to be perceived as equally loud

low & high freq sounds need greater amp to be heard at same loudness as mid freq sounds

Question 12

effects of inner ear on audition

Answer 12

cochlea converts sound to electrical impulses

responds to diff freqs along length of basilar membrane

Question 13

linear scale of auditory representation

Answer 13

measure freqs uniformly

Hz

Question 14

nonlinear scale of auditory representation

Answer 14

reflect human perception

smaller changes in lower freqs are more noticable than in higher freqs (stretch it out @ lower freqs, condense @ higher freqs)

Bark
cochlea

Question 15

frequency masking

Answer 15

each neuron responds to multiple freqs

if already firing to 1 freq (1000Hz)
can’t increase firing much to another (1100Hz)

Question 16

temporal masking

Answer 16

sounds that come in very close sequence (10-25ms) may obscure each other

Question 17

upward spread of masking

Answer 17

sounds are more easily masked when they are higher in freq than the masker

low freqs travel farther along the BM, therefore moving more of the BM

high freqs don’t vibrate as much of the BM so are not able to mask lower freqs

the traveling waves loses it’s energy after it hits the characteristic place - doesn’t vibrate beyond that

Question 18

as sound waves enter the ear, they are transformed from waves in _____ to waves in _____ to waves in ______ before before being transduced into electrical signals by the hair cells

Answer 18

air

bone

fluid

Question 19

what part of the ear conducts a kind of Fourier analysis on the incoming acoustic signal

Answer 19

basilar membrane

Question 20

auditory nerve innervates the…

Answer 20

cochlea

Question 21

what accounts for the “bump” between 2700-5000Hz

Answer 21

filtering of the pinna

resonant freqs of the ear canal

Question 22

which the bigger diff in auditory freq

1kHz to 2kHz

7kHz to 8kHz

the same

Answer 22

1kHz to 2kHz

Question 23

the neural response to a tone 2 seconds in duration will be ____ at the onset of the tone & ______ after it has been playing for 1 second

Answer 23

large

smaller

Question 24

stages up the auditory pathway

Answer 24

sound waves enters outer ear

travels through ear canal & strikes the eardrum

vibrations transferred to ossicles in the middle ear

vibrations enter cochlea, where hair cells convert them to electrical signals

signals travel through the auditory nerve to the brain

Question 25

where along a freq scale are changes in pitch more audible

Answer 25

lower freqs (100-500Hz)

due to Bark scale’s nonlinear structure – reflecting our sensitivity to pitch vibrations in that range

Question 26

Explain how engineers take advantage of our knowledge of hearing and our knowledge of speech production to enable good-sounding speech to be encoded and sent over networks with limited bandwidth.

Answer 26

Engineers apply frequency masking and equal loudness curves to reduce data, keeping only parts of the sound most perceptible to human hearing. They discard redundant data, creating clear audio with smaller file sizes, as seen in formats like MP3.