Chapter 4 - Auditory

Question 1

what are the 3 dimension of sound?

Answer 1

frequency (Hz): corresponds to our perception of pitch

amplitude (dB): corresponds to our perception of loudness

complexity: corresponds to our perception of timbre

Question 2

decibels

Answer 2

the decibel scale is a logarithmic scale that measures the strength of a sound relative to standard sound that corresponds to the absolute threshold of human hearing

Question 3

hertz

Answer 3

an ordinary listener can hear frequencies between 20 and 20,000 dB. the ear is most sensitive to tones around 1000-4000 Hz

Question 4

outer and middle ear

Answer 4

the pinna leads sound through the auditory canal to the ear drum, which starts vibrating. the vibrations are amplified through ossicles in the middle ear and subsequently transferred to the oval window

Question 5

inner ear

Answer 5

vibration of oval window sets the liquid in the cochlea in motion. hair cells on the basilar membrane detect this vibration and send impulses to the brain

Question 6

frequency theory (temporal coding)

Answer 6

the frequency of a tone is coded in the firing rate of neurons.

a tone of 300 Hz thus making these neurons fire at a rate of 300/s. for low tones this is correct however, the maximal firing rate is 1000 Hz, while we can hear much higher frequencies.

Question 7

place theory (place coding)

Answer 7

different frequencies activate different regions of the basilar membrane

Question 8

tonotopic organization

Answer 8

middle and high frequencies are coded via differential activation of the hair cells

Question 9

where is the tonotopic organization maintained?

Answer 9

it is maintained in the primary auditory cortex (A1)

Question 10

auditory pathways - from cochlea to A1

Answer 10

from the cochlea, information travels to the cochlear nucleus. most of the axons of the cochlear nucleus cells cross over to the contralateral side of the brain. both crossed and uncrossed fibers connect to the superior olivary complex. this is the first structure that receives information from both ears. next stop is the inferior colliculus followed by the medial geniculate body and finally the auditory cortex.

Question 11

sound localization

Answer 11

because our ears are on opposite sides of the head, we have stereophonic hearing where timing and loudness are the most important cues

Question 12

interaural difference in timing (ITD)

Answer 12

sound arrives sooner in the closest ear

Question 13

interaural difference in loudness (ILD)

Answer 13

sound is louder in the closest ear

Question 14

for what frequency is which cue better?

Answer 14

for high frequency tones, ILD is the best cue as high frequency sound waves cannot bend around the head

for low-frequency tones, ITD is the better cue as they can bend around objects

sound is hard to localize underwater

Question 15

is localization of sound accurate?

Answer 15

yes because;
- the shape of the auricle/pinna plays a role in vertical localization
- echos provide spatial information
- moving the head changes the combined ILD/ITD cues
- visual information informs us about sound location

Question 16

multi-sensory integration

Answer 16

combining input from multiple sensory modalities from the perceptual representation of events

Question 17

ventriloquist effect

Answer 17

when a sound is synchronized with a visual event from a different location, it often appears as if the sound emanates from their visual location

Question 18

the McGurk effect

Answer 18

seeing a speaker pronouncing a ‘g’ when the speech sound is actually a ‘b’, listeners often hear a ‘d’