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PSYO 2150: Perceptual Processes > 12: Sound Localization & Organization > Flashcards

12: Sound Localization & Organization Flashcards

1
Q

What are the two aspects of hearing for LOCATION and for ORGANIZATION? What are they similar to?

A

Location: auditory localization, hearing inside rooms.

Organization: auditory scene analysis, musical organization.

Similar to object and depth coding in the visual system.

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2
Q

Define auditory space and auditory localization.

A

Auditory space: perceive objects and events located at specific positions in space based on sound alone. Strongly complements perception of visual space

Auditory localization: localize an object’s position in space based on sound.

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3
Q

What are the terms for:

Horizontal meridian
Vertical meridian

And what is another coordinate factor?

A

Horizontal: azimuth (e.g. left, right)

Vertical: elevation (e.g. up, down)

Other coordinate: distance from the listener.

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4
Q

Azimuth and elevation are usually reported in degrees to account for _____.

A

Absolute distance.

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5
Q

People are best at localizing sounds in what location and least accurate in what location? Give errors of degrees.

A

Best for sounds directly in front. Error: ~2-3.5 degrees.

Least accurate for side and behind head. Error: ~20 degrees.

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6
Q

Primary receptor (cochlea) detects frequency of sounds, so _____ must be calculated somehow

A

Location.

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7
Q

What does the auditory system use that is akin to the visual system using depth cues?

A

Location cues.

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8
Q

What are the two types of location cues and their function?

A

Binaural cues: interaural time difference, interaural level difference.

Monaural cue: head and pinnae shape.

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9
Q

Suppose a speed of sound of ~340m/s. Using interaural time difference (ITD), how does the sound travel from the front and from the side? What are the respective ITDs?

A

Sound from the front: sound waves arrive to the left and right ears at the same time. ITD = 0.

Sound from the side: sound travels slow enough that there is a detectable difference when sound arrives at the left and right ears. ITD > 0.

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10
Q

For continuous sounds, interaural time difference could better be described as _____. Can only detect phase differences for _____.

A

Interaural phase difference; relatively long wavelengths.

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11
Q

With regards to interaural level difference (ILD), how does sound travel from the side? What does the head cast?

A

Our heads create a barrier that reduces the intensity of sounds that reach the far ear.

Head casts an acoustic shadow.

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12
Q

ILD is only available when the wavelength of the sound is ____ than the width of the head.

A

Smaller.

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13
Q

Interaural level difference is barely affected for tones below _____. Large interaural level difference for _____.

A

500Hz; higher frequency tones.

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14
Q

Both interaural time difference AND interaural level difference are used to judge _____.

A

Azimuth (horizontal meridian).

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15
Q

Location cues are frequency specific. What to ITD and ILD affect azimuth judgments for?

A

ITD: affects azimuth judgments for low frequency stimuli (~20-1000Hz).

ILD: affects azimuth judgments for high frequency stimuli (~1000-20000Hz).

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16
Q

Binaural cues don’t help much for judging _____.

A

Elevation.

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17
Q

Regarding monaural cues - before a sound stimulus enters the auditory canal, it is sometimes reflected off the head and pinnae. Interaction with the head and pinnae changes the characteristics of the sound in a specific way. What is the important difference to distinguish?

A

Sound characteristics at the source vs. sound characteristics entering the auditory canal.

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18
Q

Spectral cue can be measured with microphones at what two locations? Why are they called “spectral cues”?

A

Microphones: next to the sound source; inside the ear canal.

Called “spectral cue” because certain frequencies are increased or decreased depending on the source’s position.

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19
Q

Spectral cues are used to localize sounds at different elevations. Explain what happened in a study using pinnae reshaping during pre-treatment, day 0, day 5-19, and post-plug.

A

Pre-treatment: fairly accurate representation of azimuth and elevation.

Day 0: pinnae reshaped with plug, change in head and pinnae-related spectral cues: elevation perception eliminated.

Day 5-19: elevation perception returns.

Plug removal: elevation and azimuth perception returns to pre-treatment immediately. New representation created, rather than plasticity.

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20
Q

Regarding the physiology of ITD, barn owls use _____ and gerbils use _____.

A

Narrowly tuned ITD neurons; broadly tuned ITD neurons.

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21
Q

Barn owls use ITDs to localize sounds in _____.

A

Azimuth.

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22
Q

What are narrowly tuned ITD neurons? In what area of the brain are cells space-specific?

A

Each cell is a narrowly tuned coincidence detector.

Cells in the mesenscephalic lateralus dorsalis nucleus (MLD).

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23
Q

ITD neurons located in _____ of gerbils and other mammals are much more broadly tuned. They respond to a range of ITDs greater than what occurs in _____. Neurons respond most to sound coming from _____ side.

A

Superior olivary nucleus; natural environment; contralateral.

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24
Q

Afferent processing is _____ from the level of the superior olivary nucleus onwards.

A

Binaural.

25
Q

What or ventral stream starts in the _____ and extends to the prefrontal cortex. Responsible for _____.

A

Anterior portion of the belt; sound identification.

26
Q

Where or dorsal stream starts in the _____ and extends to the parietal and prefrontal cortices. Responsible for _____.

A

Posterior belt; sound location.

27
Q

What measure involves cooling the brain to cause temporary inactivation? What is it useful for?

A

Cryoloop inactivation. Good for behaviour tests.

28
Q

What are the consequences of inactivation for the following areas:

A1
Anterior
Posterior

A

A1: poor sound localization.

Anterior: poor sound identification.

Posterior: poor sound localization.

29
Q

For vision: receptive field location is coded _____ by the retinotopic organization that is maintained throughout processing, but other stuff like ____ and _____ are calculated.

A

Directly; motion; depth.

30
Q

For hearing: receptive field location is _____ as what? How is frequency coded?

A

As ITDs, ILDs, and spectral cues.

Frequency is coded directly.

31
Q

Define direct sounds and indirect sounds. Which are you likely to find outdoors or indoors?

A

Direct Sounds: sound waves reaching your ear traveling straight from the source.

Indirect Sounds: sound waves reaching your ear later, after they have bounced off other objects.

Outdoors: mostly direct sounds.

Indoors: mostly indirect sounds.

32
Q

Even though indirect sounds reach our ears from many different directions, they usually don’t affect sound localization. This is known as what?

A

Precedence effect.

33
Q

What is the echo threshold?

A

When the delay between direct and indirect sound exceeds a certain time we start to hear an echo.

34
Q

For brief clicks, what is the echo threshold? When is the echo threshold longer? What is the echo threshold longer for?

A

Brief clicks: echo threshold is ~5ms.

Longer when lag sound is quieter than lead sound, occurs when indirect sounds reflected off surfaces.

Longer for sounds with long durations, such as speech and music.

35
Q

The study of how sounds are reflected in rooms and the practical application for auditory psychophysics is known as what field?

A

Architectural acoustics.

36
Q

Acoustic engineers are mostly concerned with what?

A

Perception of music, particularly the auditory quality of live music.

37
Q

In architectural acoustics, what would lots of absorption do? Little absorption?

A

Lots: few reflected sound waves, and little indirect sound.

Little: many reflected sound waves, large amount of indirect sound.

38
Q

In architectural acoustics, what do room size and room shape affect, respectively?

A

Room size: affects how long it takes indirect sounds to reach the listener.

Room shape: affects the direction reflected sound waves will be sent.

39
Q

Reverberation time is the time it takes for sound to decrease to 1/1000 of its original pressure. What happens when reverberation time is too long? Too short?

A

Too long: music is perceived as muddled/blurry/echoey.

Too short: music is perceived as weak/dead.

40
Q

Along with reverberation time, what are three other measures used in architectural acoustics? Explain them.

A

Intimacy Time: time between direct and first indirect sound.

Bass Ratio: ratio of low frequencies to middle frequencies that are reflected.

Spaciousness Factor: fraction of total sound arriving at the listener that is indirect.

41
Q

The array of sound sources in the environment is called the _____.

A

Auditory scene.

42
Q

What are the two types of auditory scene? Give examples.

A

Simple: single speaker pure tone in a sound proof booth.

Complex: cocktail party.

43
Q

What must we do in auditory scene analysis?

A

Separate the stimuli produced by each sound source.

44
Q

Sound location provides 1 cue. But we can still separate sounds even if they are played through a _____.

A

Single speaker.

45
Q

Auditory grouping is based on how sounds originate in the environment. What likelihood principle is applied to sound in this instance?

A

Von Helmholtz.

46
Q

What are the six principles of auditory grouping?

A

Location: sounds created by a single source usually come from one position, or a slowly changing location. Two sounds separated in space are usually perceived as two sources.

Onset Time: if two sounds start at slightly different times they are often perceived coming from different sources.

Similarity of Timbre and Pitch: sounds that have same timbre or pitch are perceived as coming from the same source.

Proximity in time: sounds that occur in rapid succession
tend to be produced by the same source.

Good Continuation: sounds that stay constant or change smoothly are often produced by a single source.

Experience: top down influences on sound perception.

47
Q

When combined, similarity of timbre and pitch as well as proximity in time can create powerful auditory stream segregation. What is auditory stream segregation?

A

Separation of acoustic stimuli into different perceptual streams.

48
Q

Auditory stream segregation based on pitch includes what?

A

Implied Polyphony: single instrument rapidly alternating between high notes and low notes. Perceived as a high melody played by one instrument and a low melody played by another instrument.

49
Q

Auditory stream segregation also uses scale illusion/ melodic channeling. What does that entail?

A

Illusion based on similarity of pitch.

50
Q

Experience of a sequence of pitches that ‘go together’ is what?

A

Melody.

51
Q

Our perception of melody is based on _____, the rules for how notes and chords are combined in music.

A

Musical syntax.

52
Q

Event related potential (ERP) components are evoked by syntax violation. What are the ERP responses when nearby key and distant key “mistakes” are made?

A

Smaller for nearby key.

Larger for distant key.

53
Q

What are the three elements in musical timing?

A

Rhythm: time pattern of durations created by note.

Beat: timing is subdivided into equally spaced intervals.

Meter: organization of beats into measures; first beat often accented.

54
Q

Subjects listen to an ambiguous repeating sound, but hold hands and bounce to either duple or triple meter with an experimenter. When tested on which beat they heard, what were the results? Same results have been obtained when bouncing was replaced with electrical stimulation of what?

A

Subject’s report matched the bouncing rhythm on 86% of trials.

Vestibular system.

55
Q

Different languages have different STRESS PATTERNS that can lend the perception of meter to spoken phrase. When alternating short and long tones are presented to native English and Japanese speakers, what do they perceive more, respectively?

A

English: perceive short/long more often.

Japanese: perceive long/short more often.

56
Q

We are very good at seeing things that are noisy. Why is this? What neurons in primates support this?

A

Visual map of space corresponds well with our auditory map of space.

Multi-sensory neurons in primate parietal cortex.

57
Q

Sometimes vision and hearing provide disparate information. We often perceive the sound coming from its seen location. What is this effect?

A

Visual capture/ventriloquism effect.

58
Q

When studying interaction between hearing and vision, what did researchers find when they presented moving balls with silence and with a “click”?

A

Silence: 88% perceived balls moving past each other in a straight line. 12% saw balls hitting each other, deflecting in opposite directions.

“Click”: 37% straight line, 63% contact and deflection.

PSYO 2150: Perceptual Processes (13 decks)

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