Lecture 17

Question 1

On average, people can localize sounds most accurately ____ (and least accurately to their sides and behind their heads)

Answer 1

On average, people can localize sounds most accurately directly in front of them (and least accurately to their sides and behind their heads)

Question 2

Auditory localization

Answer 2

locating sounds in space

Question 3

Azimuth coordinates

Answer 3

left to right position

Question 4

Elevation coordinates

Answer 4

up and down position

Question 5

Distance coordinates

Answer 5

position relative to observer

Question 6

Location cues

Answer 6

are created based on how sound waves interact with our head/ears

Question 7

Binaural cues

Answer 7

location cues based on the comparison of the signals received by the left and right ears (intramural time and level differences) to determine the azimuth (i.e. left-right) positions of sounds

Question 8

Intramural level difference (ILD)

Answer 8

is a binaural cue related to differences in sound pressure levels reaching each ear

Question 9

Reduction in intensity occurs for high frequency sounds for the far (relative to audio source) ear, due to the head casting an __ ___

Answer 9

Reduction in intensity occurs for high frequency sounds for the far (relative to audio source) ear, due to the head casting an acoustic shadow

Question 10

acoustic shadows do not occur for ___ frequency sounds because the distance, or spacing, between waves i.e. frequency for low frequency is relatively ___, in comparison to the object casting the acoustic shadow i.e. your head

Answer 10

acoustic shadows do not occur for low frequency sounds because the distance, or spacing, between waves i.e. frequency for low frequency is relatively large, in comparison to the object casting the acoustic shadow i.e. your head

Question 11

intramural time difference (ITD)

Answer 11

is a binaural cue related to differences in the timing of when a sound reaches each ear

Question 12

When distance to each ear is the same, there is ___ ___ in ___ (___=0)

Answer 12

When distance to each ear is the same, there is no difference in timing (ITD=0)

Question 13

When the source is to the side of the observer, the times ___ ___

Answer 13

When the source is to the side of the observer, the times will differ

Question 14

__ and ___ are useful binaural cues for judging azimuth and distance

Answer 14

ILD and ITD are useful binaural cues for judging azimuth and distance

Question 15

ILD and ITD cannot reliably indicate the ___ of a sound source

Answer 15

ILD and ITD cannot reliably indicate the elevation of a sound source

Question 16

‘cone of confusion’

Answer 16

in reference to the (many) conical space(s) around the ears for which various possible pairs of points on an ‘imaginary cone’ would produce the same ITD and ILD

Question 17

monoaural cues

Answer 17

location cues based on signals reaching a single ear

Question 18

__ __ are particularly important for judging elevation, given that ILD and ITD are not effective for doing so since they may be zero in many different locations

Answer 18

monoaural cues are particularly important for judging elevation, given that ILD and ITD are not effective for doing so since they may be zero in many different locations

Question 19

The monaural cue we primarily rely on is referred to as a __ __, because it involves using information related to the distribution of intensities of a particular spectrum of frequencies experienced

Answer 19

The monaural cue we primarily rely on is referred to as a spectral cue, because it involves using information related to the distribution of intensities of a particular spectrum of frequencies experienced

Question 20

Spectral cues occur because the __ and ___ affect the intensity of sound waves entering the system

Answer 20

Spectral cues occur because the pinna and head affect the intensity of sound waves entering the system

Question 21

Sound waves are reflected off the __, as well as within the folds of the __, before stimulating the ear drum

Answer 21

Sound waves are reflected off the head, as well as within the folds of the pinnae, before stimulating the ear drum

Question 22

Frequency spectra

Answer 22

recorded by a microphone placed inside the ear for the same stimulus being played at different elevations

Question 23

Gardner and Gardner found that changing the pinnae (by smoothing out nooks/crannies using a molding compound) resulted in participants producing worse localization judgements about ___

Answer 23

Gardner and Gardner found that changing the pinnae (by smoothing out nooks/crannies using a molding compound) resulted in participants producing worse localization judgements about elevation

Question 24

Cue summary for sound source localization:
___ and ___ work for judging azimuth
___ works best for high frequency sounds
____ works best for low frequency sounds
___ cues helps us judge elevation
____ cues are also relevant i.e. vision

Answer 24

Cue summary for sound source localization:
ILD and ITD work for judging azimuth
ILD works best for high frequency sounds
ITD works best for low frequency sounds
Spectral cues helps us judge elevation
Multi-modal cues are also relevant i.e. vision

Question 25

Jeffress neural coincidence model

Answer 25

proposes that some neurons receive input from both ears and respond to ITD (are essentially ITD detectors)

Question 26

___ detectors only fire if they receive input from both axons simultaneously or in other words only fire if they receive signals originating from each ear simultaneously

Answer 26

Coincidence detectors only fire if they receive input from both axons simultaneously or in other words only fire if they receive signals originating from each ear simultaneously

Question 27

Jeffress Neural Coincidence model: Example 1- sound originating directly in front of listener

Answer 27

each ear receives stimulation at same time, resulting in transmission from each ear to the cortex to happen at same time, 'meeting' in the middle of the neural coincidence detector e.g. meeting at the middle at neuron 5. Firing of neuron 5 indicates a sound is directly in front of the listener i..e ITD=0

Question 28

Jeffress Neural Coincidence model: Example 2- sound originating to the right of a listener

Answer 28

Signal from right ear gets a 'head start' to going to cortex relative to the signal from the left ear, point which they 'meet' is skewed to left from middle e.g. instead of 5 it is at Neuron 3, firing of this neuron would indicate that sound is skewed to a right

Question 29

It may be more likely that mammals use ___ coding to encode ITD for the purpose of localizing sounds (whereas birds may sue something more akin to ___ coding)

Answer 29

It may be more likely that mammals use population coding to encode ITD for the purpose of localizing sounds (whereas birds may sue something more akin to specificity coding)

Question 30

Neurons in the left hemisphere respond best to sound from the ___, neurons in the right hemisphere respond best to sounds from the ___

Answer 30

Neurons in the left hemisphere respond best to sound from the right, neurons in the right hemisphere respond best to sounds from the left

Question 31

Evidence that A1 is involved in localization: Neff et al.

Answer 31

Cats rewarded with food for approaching boxes emitting a sound, no longer able to localize sounds after bilateral lesions to A1 (even after 5 months of training)

Question 32

Evidence that A1 is involved in localization: Nodal et al.

Answer 32

Lesioning A1 in ferrets detrimentally impacted (but did not eliminate) their ability to localize sound

Question 33

Evidence that A1 is involved in localization: Malhorta and Lomber

Answer 33

deactivating via cooling A1 in cats impairs their sound localization

Question 34

Evidence that the posterior belt is involved in localization: Recanzone

Answer 34

single-cell recordings of monkeys revealed neurons that only respond to sounds coming from particular locations in space

Question 35

Evidence that the posterior belt is involved in localization: Lomber and Malhotra

Answer 35

temporarily disputing the posterior belt again via cooling, disrupts localization. This did not affect their ability to distinguish between differences in patterns of timing related to sound stimuli

Question 36

Evidence that anterior belt is involved in perceiving sound: Rauschecker and Tian

Answer 36

while some neurons in A1 respond to pure tones, those in the anterior belt respond to more complex sounds e.g. monkey vocalizations

Question 37

Evidence that anterior belt is involved in perceiving sound: Lomber and Malhorta

Answer 37

Cooling this area in cats disrupts their ability to discern differences in timing patterns related to sound (but not localization)

Question 38

Where or dorsal stream

Answer 38

used to locate sounds

Question 39

What or ventral stream

Answer 39

used to identify sounds

Question 40

Direct sound

Answer 40

sound that reaches the listener's ears straight from the source

Question 41

Indirect sound

Answer 41

sound that is reflected off of the environmental surfaces and then to the listener

Question 42

When listener is outside, most sound is __

Answer 42

When listener is outside, most sound is direct

Question 43

Architectural acoustics

Answer 43

study of how sounds are reflected in rooms

Question 44

Reverberation time

Answer 44

time it takes sound to decrease to 1/1000th of its original pressure

Question 45

If the reverberation time is too long sound will seem '___'

Answer 45

If the reverberation time is too long sound will seem 'muddled'

Question 46

If the reverberation time is too short sound will see '___'

Answer 46

If the reverberation time is too short sound will see 'dead'

Question 47

Intimacy time

Answer 47

time between the sound leaves its source and when the first reflection arrives

Question 48

Bass ratio

Answer 48

ratio of low to middle frequencies reflected from surfaces

Question 49

Spaciousness factor

Answer 49

fraction of all the sound received by listener that is indirect

Question 50

___ spaciousness factors are typically perceived as most pleasing

Answer 50

High spaciousness factors are typically perceived as most pleasing

Question 51

Auditory scene

Answer 51

array of all sound sources in the environment

Question 52

Auditory scene analysis

Answer 52

process by which sound sources in the auditory scene are separated into individual perceptions, this does not happen at the cochlea since simultaneous sounds are processed together in the pattern of vibration of the basilar membrane

Question 53

Onset time

Answer 53

sounds that start at different times are likely to come from different sources

Question 54

Location

Answer 54

a single sound source tends to come from one location, individual sources of sound also tend to move in a smooth and continuous way