Task 8 Flashcards
A scene made of sounds (20 cards)
„Where“
- Azimuth
- ILD
Azimuth = left-right position#
ILD = difference in intensity between a sound arriving at one ear vs. the other
- correlates with the angle of the sound source
- lateral superior olives —> neurons sensitive to intensity differences between the two ears
„Where“
- Azimuth
- ITD
= difference in time between a sound arriving at one ear versus the other
- tell where sound is coming from (right/left) by determining which ear receives sound first
- in medial superior olives (MSOs) —> first place where auditory system converges inputs from both ears
„Where“
- Azimuth
- Cone of Confusion
- infinite number of cones
- same ILD and ITD
„Where“
- Elevation
- spectral cue
= information for localization is constrained in differences in the distribution of frequencies that reach each ear from different locations
„Where“
- Elevation
- pinnae&directional/head related transfer functions
- differences in the way sounds bounce around within the pinnae create different patterns of frequencies for the two locations
„Where“
- Distance
- sound level, frequency, motion parallax, reflection (direct vs. indirect)
Pathway sound travels
Hair cells (cochlea) —> nerve fibers —> cochlear nucleus —> SONIC MG (superior olivary nucleus —> inferior colliculus —> medial geniculate nucleus) —> primary auditory cortex (A1) —> core area; belt area; parabelt area
„What“
- natural sounds
- timbre —> harmonic structure + envelope
- missing fundamental = pitch remains the same, even when the fundamental or other harmonics are removed
„What“
- auditory scene analysis
= (or source segregation) processing an auditory scene consisting of multiple sound sources into separate sound images
- all sound waves from all sound sources in the environment are summed together in a single complex sound wave
—> auditory system distinguishes
„What“
- auditory scene analysis
- location
- separated based on location cues such as ITD and ILD
- use of information about where each sound source is located
„What“
- auditory scene analysis
- onset time
- sounds start at different time —> likely they came from different sources
„What“
- auditory scene analysis
- timbre and pitch
- sound with same timbre or pitch often produced by same source
„What“
- auditory scene analysis
- auditory continuity
- sound stimuli with same frequency or smoothly changing frequencies: perceived as being continuous even when interrupted by another stimulus
(like good continuation principle)
„What“
- auditory scene analysis
- experience
- when people know which melody is present, they compare what they hear to their stored schema and perceive melody
„What“
- auditory scene analysis
- auditory illusions
- e.g. continuity illusion
- by primary auditory cortex (A1)
Neural Coding for binaural cues
- Coincidence Detectors
- fire when signals arrive at neuron at the same time
- sound from straight ahead: meet in the middle
- sound from the right: meet towards left
- ITD detectors: fire to a particular ITD
Neural Coding for binaural cues
- broadly tuned neurons
- ITD curves: broader in humans than in birds
—> combining activity tuned to the left or right - population coding
- sound from left ear —> right hemisphere
- sound from right ear —> left hemisphere
- how much neurons fire indicates location of sounds (fire a lot on left side —> sound from right)
Where pathway
- posterior part of core + belt area —> prefrontal cortex
- locating sounds
What pathway
- anterior part of core + belt area —> prefrontal cortex
- identifying different types of sounds
Scale illusion
- mixtures of low and high tones to the left and right ear
- high tones: right ear
- low tones: left ear
