Chapter 12: Hearing and the Environment Flashcards
Auditory space
sounds at different locations all around
auditory localization
the locating of sound sources in auditory space
location cues
cues created by the way sound interacts with the listener’s head and ears
two types of location cues
binaural and spectral cues
3 coordinates of auditory space
azimuth, elevation, and distance (AED)
azimuth
extends from left to right
elevation
extends up and down
distance
how far the sound is from the listener
binaural cues
Use information reaching both ears to determine the azimuth of sounds
two types of binaural cues
interaural level difference and interaural time difference
Interaural level differences (ILD)
based on the difference in the sound pressure level of the sounds reaching the two ears
acoustic shadow
reduces the intensity of sounds that reach the far ear
why does interaural level difference occur
the head creates an acoustic shadow
what frequencies does ILD occur for?
high-frequency sounds
Interaural time difference (ITD)
the time difference between when a sound reaches the left ear and when it reaches the right ear
ITD if the sound is in front of the listener
ITD= 0
when is ITD larger
when sounds are located more to the side
what frequencies for ITD occur for?
low-frequency sounds
what binaural cue is more dominant?
ITD
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
cues in which information for localization is contained in differences in the distribution of frequencies that reach each ear from different locations
why do spectral cues occur?
because before the sound enters the auditory canal, it is reflected from the head and within the various folds of the pinnae
what frequencies do spectral cues occur for?
high-frequency spectra
how are different patterns of frequencies created?
Differences in the way sounds bounce around within the pinna
moulding the pinnae
makes it difficult to locate sounds along the elevation coordinate
localization performance while wearing a mould overtime
improves until day 19, when participants had learned over time to associate new spectral cues to different directions of space
what happens when moulds on the pinna are removed?
they still had excellent localization (both sets of spectral cues remained intact
The Jeffress Neural Coincidence Model
Proposes that neurons are wired so that they received signals from the two ears
Coincidence detectors
only fire when both signals coincide by arriving at the neurons simultaneously
what happens when the sound source is directly in front of the listener according to the Jeffress model?
the sound reaches the left and right ears simultaneously and signals from the left and right ears reach the coincidence detector
ITD detectors
fire best to a particular ITD
what happens when the sound source is to one side according to the Jeffress model?
that ear receives the signal first, giving its signal a head start and causing the corresponding ITD detector to fire
ITD tuning curves
plot the neuron’s firing rate against ITD
neurological basis of binaural localization in birds
based on sharply tuned neurons
coding in birds’ binaural localization
Type of place code because the ITD is indicated by the firing of neurons at a specific place in the nervous system
neurological basis of binaural localization in mammals
based on broadly tuned neurons
coding in mammals’ binaural localization
Type of population code because the ITD is determined by the firing of many broadly tuned neurons working together
Neff et al., 1956 A1 and localization experiment
placed cats in between two boxes and rewarded them if they approached the sound of the buzzer located behind one of the boxes. This task wasn’t possible for those with lesioned auditory areas, demonstrating that an intact auditory cortex is necessary for accurate localization
Nodal et al., 2010 A1 and localization experiment
showed that lesioning the primary auditory cortex in ferrets decreased, but didn’t eliminate their ability to localize sounds
Malhotra & Lumber, 2007 A1 and localization experiment
showed that cooling the auditory cortex resulted in decreased localization ability
Anterior belt area
involved in perceiving complex sounds and patterns of sound
posterior belt area
involved in localizing sounds
what auditory pathway
Associated with perceiving sounds
location of what auditory pathway
Extends from the anterior belt to the front of the temporal lobe, then to the frontal cortex
where auditory pathway
Associated with localizing sounds
location of where auditory pathway
starts in the posterior core and belt and extends to the parietal and prefrontal cortices
direct sound
sound that reaches the ears directly
indirect sound
sound that reaches the ears after bouncing off the walls, ceiling, and floors
hearing outside is based on __
direct sound
hearing inside is based on ___
direct and indirect sound
lead speaker
the actual sound source
lag speaker
a single sound reflection
precedence effect
when a single sound appears to originate from near the lead speaker because we perceive the sound as coming from near the source that reaches our ears first
architectural acoustics
the study of how sounds are reflected in rooms
architectural acoustics are largely connected with ___
indirect sound changes in the quality of the sounds we hear in rooms
main factors affecting indirect sound
- Size of the room
- The amount of sound absorbed by the walls, ceiling, and floor
absorption vs. indirect sound
More sound absorbed= little indirect sound
reverberation time
the time it takes for sound to decrease to 1/1000th of its original pressure
long reverberation time
sounds become muddled
short reverberation time
sound becomes dead
ideal reverberation time
2 seconds, but 1.5 for opera houses
intimacy time
the time between when sound arrives directly from the stage and when the first reflection arrives
bass ratio
the ratio of low frequencies to middle frequencies that are reflected from walls and other surfaces
spaciousness factor
the fraction of all of the sound received by a listener that is indirect sound
ideal dimensions for acoustics
intimacy times of 20 msec and high bass ratios and spaciousness factors were associated with good acoustics
auditory scene
the array of sound sources at different locations in the environment
auditory scene analysis (ASA)
the process by which the stimuli produced by each source are separated
auditory stream segregation
the perception of a string of sounds as belonging together
simultaneous grouping
grouping that occurs at the same time
factors that affect simultaneous grouping
- location
- onset synchrony
- timbre
- pitch
- harmonicity
simultaneous grouping and location
when two sounds are separated in space, location helps us to separate them perceptually. When a source moves, it typically follows a continuous path
simultaneous grouping and onset synchrony
if sounds start at different times, they likely came from different sources
simultaneous grouping and timbre and pitch
sounds with the same timbre or pitch range are often produced by the same source
harmonicity
when we hear a harmonic series, we infer it came from a single source
sequential grouping
grouping that occurs as sounds follow one another in time
factors that affect sequential grouping
- similarity of pitch
- auditory continuity
- experience
sequential grouping and similarity of pitch
sounds produced by the same source are usually similar in pitch
sequential grouping and auditory continuity
sounds that stay constant or change smoothly are often produced by the same sound source
sequential grouping and experience
past experience influences grouping
Deutsch’s scale illusion/ melodic channelling
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
memory schema
a representation of a familiar melody that is stored in a person’s memory
main similarity between auditory and visual perception
they both depend on guesses
perceptual grouping
putting parts together into a whole
how do tones with the same frequency activate the hair cells?
in the same way regardless of where they are coming from
where can people localize sounds most accurately
directly in front of them
where can people localize sounds least accurately?
to the sides and behind their heads
location cues in hearing vs. vision
Location cues are not contained in the receptor cells like on the retina in vision. Thus, the location of sounds must be calculated
are ILD & ITD effective for judging elevation?
ILD and ITD are not effective for judgments on elevation, since in many locations they may be zero
what do experiments on moulding the pinnae suggest?
that there might be two different sets of neurons: one for each set of cues
where are coincidence detectors located?
in the inferior colliculus
what is the mechanism behind ITD detectors?
place coding
when do broadly tuned neurons respond in the right hemisphere?
when sound is coming from the left
when do broadly tuned neurons respond in the left hemisphere?
when sound is coming from the right
a1 function
locating sound
What findings support the existence of the what and where auditory pathways?
Evidence from neural recordings, brain damage, and brain scanning
what’s the main factor that affects perception in concert halls?
reverberation time
what factors affect perception in concert halls?
- reverberation time
- intimacy time
- bass ratio
- spaciousness factor
does auditory scene analysis happen in the cochlea?
no, it doesn’t happen at the cochlea since simultaneous sounds are together in the pattern of vibration of the basilar membrane
heuristics
help perceptually organize stimuli
example of auditory scene segregation
a compound melodic line
Bregman & Campbell’s experiment
- Stimuli were in alternating high and low tones
- When stimuli are played slowly, the perception is hearing high and low tones alternating
- When the stimuli are played quickly, the listener hears two streams: one high & one low
perceptual heuristic
sounds with the same frequency come from the same source, which is usually true in the environment
proximity in time
sounds that occur in rapid succession usually come from the same source
how was proximity in time illustrated
in auditory streaming
Warren et al. experiment
- Tones were presented and interrupted by gaps of silence or noise
- In the silence condition, listeners perceive that the sound stopped during the gaps
- In the noise condition, the perception was that the sound continued behind the noise
Dowling experience and perception experiment
- The melody “Three Blind Mice” is played with notes alternating between octaves
- Listeners found it difficult to identify the song
- However, after they hear the normal melody, they can hear it in the modified version using the melody schema
- Demonstrates the effect of past experience on auditory perception
Visual capture/ the ventriloquist effect:
an observer perceives the sound as coming from the visual location rather than the source of the sound
two-flash illusion
had participants look at a screen with a stagnant light and asked them if it was flashing. If you simultaneously make them hear two beeps, they perceive two flashes.
what senses does the interaction between vision and hearing occur in?
it’s multisensory
Thaler et al., 2011
used expert blind echolocators to create clicking sounds and observed these signals activated the brain
