Topic 10: Auditory Localization and Organization Flashcards
visual vs auditory localization
3d world to 0D acoustic signal that varies in time
location in cochlea shows frequency of sound
auditory localization
task of determing source of sounds in auditory space
azimuth coordinates
elevation coordinates
distance coordinates
position L or R (easiest)
position up or down
how far is sound from observer
interaural level difference
binaural cue - needs both ears
difference in amplitude between 2 ears - clear path for one ear and other is blocked (head as acoustic barrier)
works for high frequency, has higher shadow and low bends around corner
Interaural time difference
binaural cue - needs both ears
difference in arrival time (phase) between ears based on location
due to difference in distance from sound source
if directly in front it will arrive equally
difference in sounds setting to peak - rise/fall of pressure waves is out of sync/phase
cones of confusion
ILD and ITD help determine azimuthal (L/R) direction
sounds coming straight from L is easy to detect
any point along body midline will be equidistant and unshadowed for both ears (same arrival time)
smaller cones of confusion further to sides
spectral cue
monaural cue - only requires one ear
sounds coming from different directions bounce of pinna in different ways
different signature based on elevation
King et al : spectral cue
P had eyes closed and ID whole sounds came from - initial sound location performance are accurate
- with pinna mold - elevation localization impaired due to impaired spectral cue
- performance with mold recovers by day 19 - new spectral cues are learned
Neural coincidence detectors
-only fire when both inputs occur at the same time - ITD detectors
-if it arrives to a farther left neuron it means it came from the right
set of detectors for both L and R side
narrow curve for birds and broad for mammals
Cortical areas involved in localization
-A1 core
posterior areas of belt
partietal where stream
posterior area deactivated –> cant locate sounds can ID
anterior deactivated –> can locate but not ID
auditory scene
auditory scene analysis
array of all sound sources in enviornment
-process by which sound sources in auditory scene are separated into individual perceptions
sound location
determined by ITD and ILD and spectral cues
sounds from same location are grouped
sounds from different locations are separated
onset and offset times
sounds that start/emd at same time are grouped
sounds that start/end at different times are separated
harmonic changing at different rate is perceived differently
temporal proximity
sounds near in time tend to be percieved as a group
low high low
pitch and organizing principles
sounds similar in pitch tend to be perceived as a group
auditory stream segregation
when they pass through each other they are grouped
X
temporal proximity and pitch
principles trade off based on speed and pitch
very different pitches tend to segregate as tempo increases
very similar pithces tend to stay grouped together as tempo increases
timbre
sounds with same timbre tend to be grouped
wessel demonstration - timbre and temporal proximity tradeoff
players using same instrument - we dont hear it as 2 distinct sounds - single stream (same timbre)
auditory continuity
auditory analog of good continuation
when noise bursts matches tones in level, we perceive tone continuing behind noise
picket fence with speech
experience
past experience and expectations influence auditory perception
phenomic restoration - cough makes it seem like nothing is missing
when silence we know whats missing
chromesthesia
sound to colour (auditory - visual) synesthesia
sounds create perception of colour (in moment)
involuntary and instantaneous
1/3000 - van gogh
synesthesia
1 type of perceptual phenomenon as a result of different type of sensory stimulus
developmental from birth, 1/2000
automatic
more common among children, more common in women
sound colour matches (ward et al)
synaesthete - highly consistent of colour perception across two tests when presented with a tone
control group was inconsistent which shows the perception is automatic
cross-modal stroop interference
task: p’s name colour that seeing whle hearing tone
tone was same time as colour or 150ms after
colour and tone was either congruent or incongruent with previous perception reports
synaesthete - significant stroop effect , incongruent trials led to interference and slower rxn time
possible mechanisms of stroop interfernce
- atypical direct connections between processing perceptual modalities, direction connections between A and V systems
- typical feedback pathways via multimodal convergence areas, high processing level and feedback into low visual areas
Neufeld et al: fMRI evidence
had P’s and control and listen to sounds
synaesthetes showed higher acitvation in L inferior parietal cortex (IPC) - area involved in multimodal processing
integration of auditory and visual at higher processing levels
