Topic 12: Complex Sound Perception

Question 1

Auditory Space

Answer 1

perception of where sounds are located in space

auditory space extends around a listener’s head in all direction, existing wherever there is a sound

Question 2

Auditory Localization

Answer 2

the perception of the location of a sound source

Question 3

Location Cues

Answer 3

in hearing, characteristics of the sound reaching the listener that provide information regarding the location of a sound source

Question 4

Azimuth

Answer 4

in hearing, specifies locations that vary from left to right relative to the listener

Question 5

Elevation

Answer 5

in hearing, sound locations that are up and down relative to the listener

Question 6

Distance

Answer 6

how far a stimulus is from the observer

in hearing, the distance coordinate specifies how far the sound source is from the listener

Question 7

Binaural Cues

Answer 7

sound localization cue that involves both ears

interaural time difference and interaural level difference are the primary binaural cues

Question 8

Interaural Level Difference (ILD)

Answer 8

the difference in the sound pressure (or level) between the left and right ears

this differences creates an acoustic shadow for the far ear

the ILD provides a cue for sound localization for high-frequency sounds

Question 9

Acoustic Shadow

Answer 9

the shadow created by the head the decreases the level of high-frequency sounds on the opposite side of the head

the acoustic shadow is the basis of the localization cue of the interaural level of difference

Question 10

Interaural Time Difference (ITD)

Answer 10

when a sound is positioned closer to one ear than to the other, the sound reaches the close ear slightly before reaching the far ear, so there is a difference in the time of arrival at the two ears

the ITD provides a cue for sound localization

Question 11

Cone of Confusion

Answer 11

a surface in the shape of a cone that extends out from the ear

sounds originating from different locations on this surface all have the same interaural level difference and interaural time difference, so location information provided by these cues is ambiguous

Question 12

Spectral Cues

Answer 12

in hearing, the distribution of frequencies reaching the ear that are associated with specific locations of a sound

the differences in frequencies are caused by interaction of sound with the listener’s head and pinnae

Question 13

Jeffress Model

Answer 13

the neural mechanism of auditory localization that proposed that neurons are wired to receive signals from the two ears, so that different neurons fire to different interaural time differences (ITD)

Question 14

Coincidence Detectors

Answer 14

neurons in the Jeffress neural coincidence model, which was proposed to explain how neural firing can provide information regarding the location of a sound source

a neural coincidence detector fires when signals from the left and right ears reach the neuron simultaneously

different neural coincidence detectors fire to different values of interaural time difference

Question 15

ITD Detectors

Answer 15

interaural time difference detector

neurons in the Jeffress neural coincidence model that fire when signals reach them from the left and right ears

each ITD detector is tuned to respond to a specific time delay between the two signals, and so provides information about possible locations of a sound source

Question 16

ITD Tuning Curves

Answer 16

a plot of the neuron’s firing rate against the ITD (interaural time difference)

Question 17

Anterior Belt Area

Answer 17

the front of the posterior belt in the temporal lobe, which is involved in perceiving sound

Question 18

Posterior Belt Area

Answer 18

posterior (towards the back of the brain) area of the belt area, which is an area in the temporal lobe involved in auditory processing

Question 19

Direct Sound

Answer 19

sound that is transmitted directly from a sound source to the ears

Question 20

Indirect Sound

Answer 20

sound that reaches a listener’s ears after being reflected from a surface such as a room’s walls

Question 21

Precedence Effect

Answer 21

when two identical or very similar sounds reach a listener’s ears separated by a time interval of less than about 50 to 100 ms, the listener hears the first sound reaches his or her ears

Question 22

Architectural Acoustics

Answer 22

the study of how sounds are reflected in rooms

an important concern of architectural acoustics is how these reflected sounds change the quality of the sounds we hear

Question 23

Reverberation Time

Answer 23

the time it takes for a sound produced in an enclosed space to decrease to 1/1000th of its original pressure

Question 24

Auditory Scene

Answer 24

the sound environment, which includes the location and qualities of individual sound sources

Question 25

Auditory Scene Analysis

Answer 25

the process by which the sound stimuli produced by different sources in an auditory scene become perceptually organized into sounds at different locations and into separated streams of a sound

Question 26

Simultaneous Grouping

Answer 26

the situation that occurs when sounds are perceptually grouped together because they occur simultaneously in time

Question 27

Sequential Grouping

Answer 27

in auditory scene analysis, grouping that occurs as sounds follow one another in time

Question 28

Auditory Stream Segregation

Answer 28

the effect that occurs when a series of sounds that differ in pitch or timbre are played so that the tones become perceptually separated into simultaneously occurring independent streams of sound

Question 29

Scale Illusion

Answer 29

an illusion that occurs when successive notes of a scale are presented alternately to the left and right ears

even though each ear receives notes that jump up and down in frequency, smoothly ascending or descending scales are heard in each ear

also called melodic channeling

Question 30

Melody Schema

Answer 30

a representation of a familiar melody that is stored in a persons memory

existence of a melody schema makes it more likely that the tons associated with a melody will be perceptually grouped

Question 31

Multisensory Interactions

Answer 31

use of a combination of senses

an example for vision and hearing is seeing a person’s lips move while listening to the person speak

Question 32

Visual Capture

Answer 32

when a sound is heard coming from a seen location, even though it is actually originating somewhere else

also called the ventriloquism effect

Question 33

Two-Flash Illusion

Answer 33

an illusion that occurs when one flash of light is presented, accompanied by two rapidly presented tones

presentation of the two tones causes the observer to perceive two flashes of light

Question 34

Speechreading

Answer 34

process by which deaf people determine what people are saying by observing their lip and facial movements

Question 35

What are interaural level differences?

Answer 35

move azimuth (horizontal direction of sound source) off to one side

one ear falls into “sound shadow”: sounds are bent around the head, or are diffracted by the edge of the head

intensity difference between ears used at location cue

difference may be as large as 30 dB

affects higher frequencies

Question 36

What are interaural time differences?

Answer 36

difference in arrival times of the sound to each ear

neurons found in auditory cortex and superior olives that respond to certain interaural time differences

differences as small as 10 us detected

affects lower frequencies

Question 37

What are phase differences?

Answer 37

difference in phase between two waves at a point in time

e.g., two tones at 1000 Hz (1 cycle takes 1.0 ms); if arrival times differ by 0.5 ms, phase difference = 180 degrees

works better for lower frequencies

Question 38

How does the pinna affect auditory localization?

Answer 38

delays/amplifies some frequencies coming from certain directions/elevations

may decrease intensity of some mid-range frequencies – but only if the source is behind the head

Question 39

What is precedence effect?

Answer 39

present two identical sounds from two speakers in different locations

at shorter delays (</= 2 ms and for simultaneous presentation), perception is of one sound located between the sound sources (fusion)

at longer delays (35 ms), two separate sounds are perceived (echo threshold)

if sounds are separated by a delay of 5 to 20 ms, sound is perceived to be coming from leading speaker only

lagging sound is suppressed for reasons not well understood

facilitates hearing in a complex acoustic environment

Question 40

What is echolocation?

Answer 40

some animals send out ultrasonic waves (e.g., bats)

reflections off objects used to locate obstacles, prey, etc.

seems to be used by visually impaired people, but can learned by anyone

Question 41

What was the Ammons, Worchel, & Dallenbach (1953) experiment on echolocation?

Answer 41

blindfolded participants

walked toward obstacles at 6, 12, 18, 24, or 30 feet

with practice, they could locate and avoid the obstacles

but not when wearing earplugs

Question 42

What was the Kellogg (1962) experiment on echolocation?

Answer 42

standard stimulus: wooden disk (12’ diameter) placed 20 feet away

distance of comparison disk was varied

blind participants were allowed to make any noise to determine distance of comparison

differences of 2 feet were reliably made

Question 43

What is reverberation?

Answer 43

reflection of sound by walls, ceiling, and floor

“reverb” is less as sound source is approached

for optimal aesthetics, amount of direct and indirect (reflected) sound must be balanced

Question 44

What is reverb time?

Answer 44

time for sound to decrease to 1/1,000th of original pressure

too short reverb time: music sounds “dead”

to long: music sounds “muddy”

concert hall should have reverb time 1.5-2.0 seconds

Question 45

What were the causes of the problems in the Lincoln Center’s Philharmonic Hall in NYC?

Answer 45

reflecting ceiling panels were too small and dispersed; absorbed too much low-frequency sound

“seat-dip effect”: significant deterioration of bass reverberation as sound passes over rows of seats

to increase capacity, concave sidewalls were built; these caused echoes and distortions

spatial impression of music is highly dependent on reflections from sidewalls; makes you feel enveloped by an orchestra

Question 46

What is primitive grouping?

Answer 46

continuous flow of sound analyzed into separate chunks and grouped (like Gestalt laws)

important variables include intensity, temporal change, frequency change, location, timbre, etc.

grouping occurs according to: similar patterns over time (sequential grouping), similar frequency spectra (simultaneous grouping)

results in separate auditory streams: groups of sounds that seem to belong together

Question 47

What is schema-driven grouping?

Answer 47

higher-level knowledge guides the grouping and listening processes

attention allows a selected sound to be processed more

sound input is analyzed for particular pattern(s)

e.g., mechanic listening for an engine clicking vs. clunking

Question 48

What is absolute pitch?

Answer 48

definition: extreme accuracy (at least 90%) in identifying an isolated musical note without a reference tone – not literally “perfect pitch”

rate of occurrence is 1 in 10,000 people

may include ability to name the key of a piece of music

it’s more difficult to produce (i.e., sing) a given note than to identify a heard one

influenced by timbre and tone chroma: similarity shared by musical tones that have the same name

errors often are in naming the octave, not the note

most with this ability began studying music before age 5

may be a critical period for absolute pitch development

may have genetic basis

Question 49

What are the difficulties in studying music and the brain?

Answer 49

observations of patients with brain injuries are contradictory

brain imaging studies have been incomplete

music is complex, having melody, harmony, rhythm, and timbre

large individual differences

Question 50

What is the case study of Maurice Ravel?

Answer 50

in 1933, the French composer began to exhibit symptoms of focal cerebral degeneration, a disorder in which discrete areas of brain tissue atrophy

conceptual abilities remained intact: could still hear and remember his old compositions and play scales – but could not write music

“this opera is here, in my head. I hear it, but I will never write it. It’s over. I can no longer write my music”

suggests that the brain does not have a specific center for music

Question 51

What was the Altenmuller (2004) study on music and brain areas?

Answer 51

primary and secondary auditory cortices handle early stages of music perception (e.g., pitch and intensity)

secondary auditory cortex processes more complex music patterns: harmony, melody, rhythm

tertiary regions thought to integrate patterns into a coherent musical whole

beyond this are associations areas (e.g. Wernicke’s area)

left hemisphere processes intervals (distance between tones) and rhythm (durations of a series of notes)

right hemisphere recognizes holistic traits including meter (regular beat; e.g., three-quarter time) and melodic contour (pattern of rising and falling pitches)

Question 52

What was the Weinberger & colleagues study on neural plasticity and music?

Answer 52

measured tuning curves of neurons in auditory cortex of neurons in guinea pigs

paired a specific tone with mild foot shock

found neurons that had shifted their tuning curves to the frequency of the CS tone; became stronger over time

learning can retune the brain so that more cells respond to behaviorally important sounds

Question 53

What was the Pantev & colleagues (1998)?

Answer 53

musicians listened to a piano playing

about 25% more of their left-hemisphere auditory regions respond than in nonmusicians

specific to musical tones; does not occur with similar nonmusical sounds

this effect is greater, the younger the age at which music lessons began

Question 54

What was the Halpern & Zatorre (1999) study on hearing and imagery?

Answer 54

PET scanned brains of nonmusicians who listened to music, or imagined hearing the same piece of music

same areas in temporal lobes activated both when listening to the melodies and imagining them