chapter 10-hearing in the environment Flashcards
large portion of processing is done ___ A1
before
differences in structure of auditory and visual systems from
evolutionary reasons, subcortical vs cortical
primary auditory cortex is mapped
tonotopically
primary auditory cortex
A1; 1st area within temporal lobes of brain responsible for processing acoustic information; tones, frequencies
belt area
adjacent to A1 with inputs where neurons respond to more complex characteristics of sounds, change in frequency over time
parabelt area
lateral and adjacent to belt area, complex sounds and integration across senses
what
temporal lobe (hearing and vision); identification and interpretation of sound
where
subcortical-superior olive; location
monaural pathway in the inferior colliculi may carry info about
what the sound is
binaural responses in the superior olive contains special neural circuits that computes ___ a sound originates
where
Monaural pathway
single ear processing to the superior colliculus, tone based, nature of the sound itself
MGN is like the
LGN
binaural reponses
location; comparison across 2 different ears; superior olive
how do you locate a sound
sound enters ears the same regardless of location; will be closer to one ear than the other
interaural time differences (ITD)
the difference in time between a sound arriving at one ear versus the other
azimuth
the angle of a sound source on the horizon relative to a point in the center of the head between the ears
azimuth is measure in ___, with 0 being ___ and 180 being ___
degrees, straight ahead, directly behind
azimuth angle is __ to the right and ___ to the left
positive, negative
if sound comes from directly in front of or behind someone LTD’s are ____
absent
LTD’s are greatest when
coming from one side to the other
size of circles is due to
temporal difference in location of sound
time unit of ITD
microseconds
threshold of ITD
~10-20 microseconds
ITD with what aspect of sound
phase
interaural level difference (ILD)
the difference in level (intensity) between a sound arriving at one ear versus the other
for frequencies greater than 1000 Hz, the head block some of the energy reaching the ___ ear
opposite
ILD is largest where; and nonexistent where
largest at 90 and -90; none at 0 and 180
ILD generally correlated with ___ of sound source, but not the same as ITD
angle;due to frequency, irregular shape of the head
level
amplitude
ILD remains ___ for low frequencies; __ correlation
constant; low
high frequency, __ correlation
high
low frequency sounds use
ITD for best info
high frequency sounds use
both ILD and ITD
phase
precise timing
superior olive
relay station in the brain stem where inputs from both ears come together; MSO and LSO; where llocation info is processed
medial superior olive
ITDs
lateral superior olive
ILDs; excitatory from ipsilateral and inhibitory from contralateral ear; sum across
cone of confusion
region of positioins in space where all sounds produce the same ITDs and ILDs; problem of ambiguous info
to solve the cone of confusion problem
turn head to disambiguate ILD/ITD similarity
HRTF (head related transfer function)
filtering properties of our hed and ear; specific to individual; no physical movement, experience
echolocation
using the returned/reflected sound that was produced by the observed in order to determine location and shape of objects in the world; gives 3D info of the world to blind person and they process it in the visual system
sound localization uses
auditory distance perception
simplest cue for auditory distance perception
relative intensity of sound; sounds are less intense with greater distance
inverse-square law
as distance from a source increases, intensity decreases faster such that decrease in intensity is the distance squared; best within 1 meter of head
spectral composition of sounds
higher frequencies decrease in energy more than lower frequencies as sound waves travel from source to one ear
relative amounts of direct energy vs reverberant energy
reverberant-more auditory copies the further you are away
harmonics
complex sounds have more than 1 frequency
fundamental frequency
lowest frequency of harmonic spectrum
missing fundamental effect
the pitch listeners hear corresponds to the fundamental frequency, even if it is missing
lowest level fundamental aspect fill info
in
if you have a sound and sum together, the output of summation has a
peak at 4 ms
timbre
psychological sensation by which a listener can judge that two sounds with the same fundamental loudness and pitch are dissimilar
in natural situation
acoustic environment is busy and has multiple sound sources
source segregation (auditory scene analysis)
processing an auditory scene consisting of multiple sources into separate sound images; gestalt grouping by similarity and proximity
source segregation; what
frequency content/timbre; similarity
source segregation; where
location of the sound source; proximity
grouping by timbre
tones that have increasing and decreasing frequencies will group either by pitch or timbre
grouping by onset
when sounds being at the same time, they appear to be coming from the same sound sound
how do we know that listeners really hear a sound as continuous
principle of good continuation
principle of good continuation
in spite of interruptions, one can still “hear” a sound
behavioral evidence for principle of good continuation
can’t tell if sound glide is present or not; brain fills in missing info if blocked by noise
physiological evidence for principle of good continuation
A1 metabolic activity consistent with perceived sounds, even if absent; single cell recordings in monkey same to real and restored tones
restoration of complex sounds
listeners use “higher order” sources of info, not just auditory info to restore missing segment
gaps in sound stream are ___ detrimental if filled with noise rather than silence
less
with noisy gaps
cant even reliably tell where the gaps were specifically
