Topic 12: Complex Sound Perception Flashcards
Auditory Space
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
Auditory Localization
the perception of the location of a sound source
Location Cues
in hearing, characteristics of the sound reaching the listener that provide information regarding the location of a sound source
Azimuth
in hearing, specifies locations that vary from left to right relative to the listener
Elevation
in hearing, sound locations that are up and down relative to the listener
Distance
how far a stimulus is from the observer
in hearing, the distance coordinate specifies how far the sound source is from the listener
Binaural Cues
sound localization cue that involves both ears
interaural time difference and interaural level difference are the primary binaural cues
Interaural Level Difference (ILD)
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
Acoustic Shadow
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
Interaural Time Difference (ITD)
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
Cone of Confusion
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
Spectral Cues
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
Jeffress Model
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)
Coincidence Detectors
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
ITD Detectors
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
ITD Tuning Curves
a plot of the neuron’s firing rate against the ITD (interaural time difference)
Anterior Belt Area
the front of the posterior belt in the temporal lobe, which is involved in perceiving sound
Posterior Belt Area
posterior (towards the back of the brain) area of the belt area, which is an area in the temporal lobe involved in auditory processing
Direct Sound
sound that is transmitted directly from a sound source to the ears
Indirect Sound
sound that reaches a listener’s ears after being reflected from a surface such as a room’s walls
Precedence Effect
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
Architectural Acoustics
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
Reverberation Time
the time it takes for a sound produced in an enclosed space to decrease to 1/1000th of its original pressure
Auditory Scene
the sound environment, which includes the location and qualities of individual sound sources
Auditory Scene Analysis
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
Simultaneous Grouping
the situation that occurs when sounds are perceptually grouped together because they occur simultaneously in time
Sequential Grouping
in auditory scene analysis, grouping that occurs as sounds follow one another in time
Auditory Stream Segregation
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
Scale Illusion
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
Melody Schema
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
Multisensory Interactions
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
Visual Capture
when a sound is heard coming from a seen location, even though it is actually originating somewhere else
also called the ventriloquism effect
Two-Flash Illusion
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
Speechreading
process by which deaf people determine what people are saying by observing their lip and facial movements
What are interaural level differences?
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
What are interaural time differences?
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
What are phase differences?
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
How does the pinna affect auditory localization?
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
What is precedence effect?
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
What is echolocation?
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
What was the Ammons, Worchel, & Dallenbach (1953) experiment on echolocation?
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
What was the Kellogg (1962) experiment on echolocation?
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
What is reverberation?
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
What is reverb time?
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
What were the causes of the problems in the Lincoln Center’s Philharmonic Hall in NYC?
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
What is primitive grouping?
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
What is schema-driven grouping?
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
What is absolute pitch?
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
What are the difficulties in studying music and the brain?
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
What is the case study of Maurice Ravel?
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
What was the Altenmuller (2004) study on music and brain areas?
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)
What was the Weinberger & colleagues study on neural plasticity and music?
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
What was the Pantev & colleagues (1998)?
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
What was the Halpern & Zatorre (1999) study on hearing and imagery?
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
