Chapter 12

Question 1

What is sound localization?

Answer 1

The ability to identify the location of a sound source in a sound field

Question 2

What is the precedence effect?

Answer 2

When a sound is followed by another sound separated by a short time delay, listeners perceive as a single auditory event.

Question 3

What is auditory stream analysis?

Answer 3

The ability to separate each of the sound sources and sperate them in space.

Question 4

What is perceptual grouping?

Answer 4

Putting parts together into a whole

Question 5

What is an auditory scene analysis?

Answer 5

Figuring out where sounds are coming from within a scene

Question 6

What is auditory space?

Answer 6

Surrounds an observer and exists wherever there is sound.

Question 7

How do tones with the same frequency activate the cochlea?

Answer 7

They activate the cochlea (hair cells) in the same way regardless of where they are coming from.

Question 8

Explain the three coordinates used by researchers to study how sounds are localized in space:

1. Azimuth coordinates:
2. Elevation coordinates:
3. Distance coordinates:

Answer 8

1. Azimuth coordinates:
   - Position left to right
2. Elevation coordinates:
   -Elevation coordinates
3. Distance coordinates:
   - Position from observer

Question 9

Which two ways can people localize sounds? (And which is accurate and which is not)

Answer 9

1. Directly in front of them most accurately
2. To the sides and behind their heads least accurately

Question 10

Are location cues contained in receptor cells (like in the retina)?

Answer 10

No, location for sounds must be calculated

Question 11

What are binaural cues?

Answer 11

Location cues based on the comparison of the signals received by the left and right ears.

Question 12

What is interaural time difference?

Answer 12

Difference between the times that sounds reach the two ears.

Question 13

What happens when the distance to each ear is the same?

Answer 13

No difference in time.

When a source is at the side of an observer there will be differences in time.

Question 14

What is interaural level difference?

Answer 14

Difference in sound pressure level reaching the two ears

Question 15

How do we use sound pressure / intensity for determining location?

Answer 15

Reduction in intensity happens in for ear.

Why? head casts an acoustic shadow

*Note: head shadow doesn’t happen for low frequency sounds

Question 16

What is the cone of confusion?

Answer 16

Imaginary cone extending outward from each ear, representing sound source locations that produce interaural differences.

Question 17

Explain the experiment with interaural level difference and interaural time difference:

(Pinne molds)

Answer 17

Have them listen normally

Mold put in pinnae

poor at detecting elevation, fine for Azimuth

Slowly caught up with their original results

Conclusion: different neurons do each set of cues.

Question 18

What is the Jeffress Neural Coincidence model?

Answer 18

Signals from both ears
Both hit a spot and that indicates where the sound is.
(In Inferior colliculus)

ITD detectors: place code

Question 19

What is coding for localization based on?

Answer 19

Broadly tuned neurons

Location of a sound is indicated by relative responses of these two types of broadly tuned neurons.

Question 20

Where do sounds from the left go?

Answer 20

The right hemisphere

Question 21

Where do sounds from the right go?

Answer 21

The left hemisphere

Question 22

What does area A1 do?

Answer 22

Involved in locating sound

Question 23

What does the posterior belt area do?

Answer 23

Involved in location sound

Question 24

What does the Anterior belt do?

Answer 24

Involved in perceiving sound

Question 25

Where does the what or ventral stream start?

Answer 25

Starts in the anterior part of the core and extends to the prefrontal cortex

Question 26

Where does the where or dorsal stream start?

Answer 26

Starts in the posterior core and extends to parietal and prefrontal cortices (locate sound)

Question 27

How did we find the ventral and dorsal stream?

Answer 27

Found with neural recordings, brain damage, and brain scanning.

Question 28

What is direct sound?

Answer 28

Sound that reaches listeners ears straight from the source

Question 29

What is indirect sound?

Answer 29

Sound that is reflected off of environmental surfaces and then to the listeners

Question 30

When outside we tend to hear _____ sound.

Answer 30

Direct

Question 31

When inside we tend to hear _____ sound.

Answer 31

Indirect and direct

Question 32

Explain the experiment with a lead and lag speaker? (The precedence effect)

Answer 32

When sound is from the lead speaker with a long gap then lag. Listeners hear two sounds When the delay is 5:20 msec, only hear sound from the lead speaker

Question 33

How is reverberation time used on concert halls? (too long too short and the ideal time)

Answer 33

If too long: sound is 'muddled' if too short: sound is 'dead' Ideal time: 2 seconds

Question 34

What is reverberation time?

Answer 34

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

Question 35

What is intimacy time? (used in concerts)

Answer 35

Time between when a sound leaves the source and when the first reflection arrives. (best time = 20 ms)

Question 36

What is bass ratio?

Answer 36

Ratio of low to middle frequencies reflected from surfaces (best ratio = high)

Question 37

What is spaciousness factor?

Answer 37

Fraction of all the sound received by a listener that's indirect. (high spaciousness factor is best)

Question 38

What is the auditory scene?

Answer 38

Array of all sound sources in the environment

Question 39

What is auditory scene analysis?

Answer 39

Process of separating sound sources into individual perceptions (doesn't happen at the cochlea)

Question 40

1. Explain the parts of simultaneous grouping? (how we group / distinguish sounds) What is onset time? What is location? What is the similarity of timbre and pitch?

Answer 40

What is onset time? -Sounds that start at diff times are likely from diff sources What is location? -A single sound source tends to come from one location and move consistently What is the similarity of timbre and pitch? Similar sounds = grouped

Question 41

2. Explain the parts of sequential grouping Experiment (with tones) Galloping Scale illusion and melodic channeling And noise experiment by warren

Answer 41

Experiment (with tones): -When play high and low tones slowly a person hears high and low tones that alternate -When played quickly, a person hears two streams Galloping: -Merging two sounds together when they start sounding the same Scale illusion and melodic channeling: - Notes enter left ear -Notes enter right ear -Brain will group those similar in pitch as being the from the same source (usually true in the environment) And noise experiment by warren: Sounds Either a pause or noise interrupts Silence: thought sound stopped Noise: thought sound continued behind noise

Question 42

3. Explain the effect of past experience three blind mice experiment

Answer 42

If the three blind mice are played at diff octaves - its hard to identify the song But if you play the normal one before - they can identify it.

Question 43

What is visual capture / the ventriloquist effect?

Answer 43

An observer perceives the sound as coming from a visual location rather then the source of sound

Question 44

What is the two flash illusion?

Answer 44

Two beeps and one flash simultaneously Will perceive two flashes

Question 45

What can blind people use to help see?

Answer 45

Echolocation to make clicking sounds and observe the echoes on the environment. Activates similar parts of the brain as visual / hearing