Task 8- the auditory scene Flashcards Preview

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Flashcards in Task 8- the auditory scene Deck (21)
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1
Q

How is having 2 ears useful for localizing sound in space?

A
  1. Because pressure waves dont reach both ears at the same time (ITD)
  2. Because sound intensity is greater at the ear closer to the sound source (ILD)
2
Q

Interaural Time Difference (ITD)

A

The difference in time between the sounds arriving at one ear and the other, works best at low frequencies

3
Q

Azimuth

A

The angle of a sound source on a horizontal plane relative to our head in the center
Is read clockwise, straight ahead is 0, behind the head is 180, the left part is then descending with a minus (-160, etc)

4
Q

When is the ITD the smallest, when the largest?

A

The smallest ITD occurs at 0 and 180 degree azimuth, the largest at 90 and -90 degree azimuth

5
Q

Physiology of ITD

A
  • Information from both cochleas reaches the cochlear nucleus and travels then to both LSO ( Lateral superior olive) and MSO ( medial superior olive) of each side
  • according to the Jeffress modell, there are ITD detectors, that fire when information received indicates a specific point (place coded, only birds)
  • mammals have broadly tuned neurons with a distribution code -> response is a combination of many neurons
6
Q

The what pathway

A

It extends from the anterior core and belt to the prefrontal cortex, responsible for identifying sound (these neurons respond very good to complex sounds)

7
Q

The where pathway

A

It extends from the posterior core and belt to the prefrontal cortex, responsible for localizing sound in space (these neurons have a much better spatial tuning, than A1)

8
Q

Interaural level difference (ILD)

A
  • Sounds are more intense at the ear closer to the sound source, because the head works as an acoustic shadow
  • correlates with azimuth in a similar matter as ITD (biggest at 90/-90)
  • only works for frequencies above 1000hz
9
Q

Physiology of ILD

A
  • neurons to identify ILD are found in the LSO (lateral superior olive)
  • they receive excitatory input from the ipsilateral cochlea and inhibitory input from the contralateral cochlea
  • these inputs compete, the neurons fire stronger at the cochlea closer to the sound source
  • thus, the side closer to the sound source has stronger excitation, and enhanced inhibition contralateral
10
Q

Cones of confusion

A

A region in space, which extends around our head, and has the same ILD and ITD for every location in this region, making it hard to localize the sound source
-> moving our head solves this problem

11
Q

Directional transfer function (DTF)

A
  • Describes how pinna, ear canal, head and torso change the intensity of sounds with different frequencies that arrive at each ear from different locations in space
  • Changes over time due to growth of head, and ear, experience is important in using DTF to localize sounds
12
Q

The pinna as a cue for sound localization

A
  • The pinna is unique for individuals and provides additional information about the sounds localization
  • It enhances some frequencies different than others, and some locations will be reflected differently than others from it, thus it helps localizing sounds and identifying them
13
Q

Auditory distance perception

A
  • Relative intensity as a cue, because sound becomes less intense with distance (inverse-square law)
  • spectral composition as a cue, as air dampens high frequency pressure waves more than low frequency (only noticeable for distances over 1000 meter)
  • the relative amounts of direct vs indirect/ reverbant sound, because the closer a sound is the more direct the energy is, the farther away, the more reverbant energy
14
Q

Auditory scene analysis/ source segregation

A

distinguishing different sounds in an auditory scene

15
Q

Spatial seperation between sounds (cue for auditory scene analysis)

A

sounds that come from the same location in space can be treated as if the arose from the same sound source

16
Q

spectral/ temporal segmentation (cue for auditory scene analysis)

A

sounds with a similar pitch are being treated as coming from the same source and put into one “auditory stream”. -> auditory stream segmentation

17
Q

Grouping by timbre (cue for auditory scene analysis)

A

sounds with the same timbre usually arise from the same sound source

18
Q

Grouping by onset (cue for auditory scene analysis)

A

sound components that begin at the same time will be tend to be heard as coming from the same sound source

19
Q

getting familiar with sounds (cue for auditory scene analysis)

A

familiar sounds (like one’s name) will be easier to pick up than unfamiliar sounds

20
Q

Continuity and restoration effect (cue for auditory scene analysis)

A

our brain is able to restore sound that is interrupted as if it was continuing

21
Q

acoustic startle reflex

A

very rapid motor response to a sudden sound, very few neurons involved, onset around 10ms after sound, anxiety can enhance motor response