Task 8 a scene made of sounds

Question 1

What pathway

Answer 1

Starts in anterior part of core and belt and extends to prefrontal cortex.
o Responsible for identifying different types of sounds.
o Neurons in anterior belt respond to more complex sounds. ´
o Deactivating anterior auditory areas disrupts ability to distinguish two patterns of sounds but does not affect sound localization

Question 2

Where pathway

Answer 2

Starts in posterior part of core and belt and extends to prefrontal cortex.
o Associated with locating sounds.
o A1 is important for localization but neurons in posterior belt have better spatial tuning than those in A1.
o Deactivating posterior auditory areas disrupts ability to localize sounds but does not affect sound identification.

Question 3

auditory scene

Answer 3

Acoustic environment

Question 4

Source segregation/auditory scene analysis

Answer 4

: Processing an auditory scene consisting of multiple sound sources into sperate sound images

Question 5

Spatial segregation

Answer 5

Sounds that emanate from the same location in space can typically be treated as if the arose from the same source

Question 6

Spectral/temporal segregation

Answer 6

sound with the same or similar pitch are more likely to be treated as coming from the same source

Question 7

Auditory stream segregation

Answer 7

The perceptual organization of a complex acoustic signal into separate auditory events for which each stream is heard as a separate event

Question 8

Interaural time difference (ITD)

Answer 8

The difference in time between a sound arriving at one ear versus the other (low frequencies more efficient)

Question 9

Azimuth (ITD)

Answer 9

The angle of a sound source on the horizontal plane relative to a point in the centre of the head between the ears. Azimuth is measured in degrees, with 0 degrees being straight ahead. The angle increases clockwise toward the right, with 180 degrees being directly behind, we can detect delays of little as 10 us (1 degree)

Question 10

Medial superior olive (MSO) (ITD)

Answer 10

a relay station in the brain stem where inputs from both ears converge to detection of the interaural time difference

Question 11

Interaural level difference (ILD)

Answer 11

The difference in level (intensity) between a sound arriving at one ear versus the other (high frequency)
o Sounds are louder at the ear which is closer to the sound source
o The ILD is largest at 90 and -90 degrees, and it is non-existent at 0 and 180 degrees
o Less precise because of the irregular shape of the head compared to ITD
o Head blocks high-frequency sounds more efficient than low-frequency sounds

Question 12

Lateral superior olives (LSOs) (ILD)

Answer 12

A relay station in the brain where inputs from both ears contribute to detection of the interaural level difference, excitatory comes ipsilateral and inhibitory comes contralateral

Question 13

Cone of confusion

Answer 13

A region in space where all sounds produce the same time and level (intensity) differences (ITDs and ILDs)

Question 14

Intensity (distance)

Answer 14

sound becomes less intense over space

Question 15

Inverse-square law (distance)

Answer 15

A principle that as distance from a source decreases faster such decrease in intensity is equal to the distance squared. This general law also applies to optics and other forms of energy

Question 16

Distance prediction

Answer 16

good for up to 1 meter farer distances are often underestimated, especially good for moving objects, e.g. hearing a frog hopping in your direction

Question 17

Relative amount of direct versus reverberant energy (distance)

Answer 17

At close distance more direct energy hits your ear, where as reverberant energy provides a greater proportion of the total when the sound source is farther away

Question 18

Pinnea (localisation)

Answer 18

tunnels certain frequencies more efficient the others

Question 19

Body (localisation)

Answer 19

especially the upper torso affect which frequencies reach the ear most easily

Question 20

Directional transfer function (localisation)

Answer 20

A measure that describes how the pinna, ear canal, head, and torso change intensity of sounds with different frequencies that arrive at each ear from different locations in space (azimuth and elevation)

Question 21

Elevation

Answer 21

the bottom to top localization

Question 22

Timbre

Answer 22

The psychological sensation by which a listener can judge that two sounds with the same loudness and pitch are dissimilar. Timber quality is conveyed by harmonics and other high frequencies
o Perception of timber is related to the relative energies of different acoustic spectral components

Question 23

Attack (timbre)

Answer 23

The part of a sound during which amplitude increases (onset)

Question 24

Decay (timbre)

Answer 24

The part of a sound during which amplitude decreases (offset)

Question 25

Grouping by onset

Answer 25

sound components that begin at the same time are likely to be heard as they come from the same source

Question 26

Similarity (gestalt)

Answer 26

sounds that are similar to each other tend to be grouped into streams

Question 27

Common fate (gestalt)

Answer 27

grouping sounds by onset

Question 28

Familiarity (gestalt)

Answer 28

you get used to certain sounds which makes it easier to sperate them from others (e.g. your name)

Question 29

Good continuation (gestalt)

Answer 29

the continuous auditory stream is heard to continue behind the masking sound (perceptual restoration effect)

Question 30

Precedence effect

Answer 30

If there is only a short delay between two sounds, then sound is perceived to come only from the that started playing the sound first. It means that we perceive sound as coming from its source, rather than from many different directions at once.

Question 31

JEFFRESS NEURAL COINCIDENCE MODEL OF AUDITORY LOCALIZATION (Birds)

Answer 31

Model that proposes that neurons are wired so they each receive signals from two ears

Question 32

Coincidence detectors

Answer 32

Neurons that only fire when both signals coincide by arriving at same time at neuron

Question 33

How does coincidence of auditory localisation work

Answer 33

 Axons transmit signals from left and right ear to neurons (= circles).  Sound in front – Signals start simultaneously in channels and meet at middle neuron (5), causing it to fire.  Sound to the right – Signal starts in right channel first and signals meet at neuron closer to left ear (3), causing it to fire.

Question 34

ITD curves explained

Answer 34

When ITD tuning curves are measured in humans, curves are broader than in birds. Therefore, it was proposed that coding for localization is based on broadly tuned neurons for humans and sharply tuned neurons for birds.  Broadly tuned neurons in right hemisphere respond when sound is coming from left, while those in left hemisphere respond when sound is coming from right.  How much these neurons fire indicates the location of sound. If sound is in left side, right hemispheric neurons respond faster.  Distributed code – Code of localization for mammals because ITD is determined by firing of many broadly tuned neurons working together.