Problem 8 Flashcards
Auditory space
Sounds of different locations
–> exists all around
Auditory localization
Locating of sound sources in auditory space
–> sounds stimulate the cochlea based on their sound frequencies, which causes a pattern of nerve firing
Localization cues
a) binaural cues
b) monaural cues
Azimuth/
Horizontal
Dimension that extends from left to right
Elevation/
Vertical
Dimension that extends up and down
Distance
Distance of the sound source to the listener
Binaural cues
Use information reaching both ears to determine the azimuth of sounds
–> sounds that are of to the side, reach one ear faster and is therefore louder there
Inter aural time difference
ITD
Difference between WHEN a sound reaches the left ear + when it reaches the right one
- -> ITD locates low frequencies
- -> judge the azimuth
Inter aural level difference
ILD
Difference in the SOUND PRESSURE level/ the level of sound reaching the two ears
- -> ILD locates high frequencies
- -> judge the azimuth
Acoustic shadow
Refers to the head being a barrier
–> reduces the intensity of high frequency sounds that reach the far ear
Cone of confusion
Points on this cone have the same ILD + ITD
–> thus, ITD + ILD provide ambiguous info about the elevation of a sound source
Monaural cues
Use information of only one ear to determine the elevation of sounds
Spectral cue
Primary monaural cue
–> info for localization is contained in the differences in the distribution of frequencies that reach each ear
Why are there differences in frequency distribution reaching each ear ?
Because before the sound enters the auditory canal, it is reflected from the head + within the various folds of pinnae
Jefress Model of auditory localization
Neurons are wired so they each receive signals from the 2 ears
–> at the beginning neurons only receive signals from either ear, if signals then reach a neuron together it will fire
Coincidence neurons
Neurons that only fire when both signals coincide by arriving at the neuron simultaneously
–> each neuron responds best to a specific ITD
—> presented in the superior + inferior colliculei
Binaural localization
Based on
a) sharply tuned neurons for birds
b) broadly tuned neurons for mammals
Place code
ITD is indicated by the firing of neurons at a specific place
–> code for birds
Distributed code
ITD is determined by the firing of many broadly tuned neurons working together
–> code for mammals
=> broadly tuned neurons in the right hemisphere respond best to sound coming from the left and vice versa
Which cortical areas provide information about the location of sound sources ?
- A1 area to a small extent
- Neurons in the belt area provide most precise + detailed info
Auditory what pathway
Starts in the anterior part of the core + belt
- -> extends to the prefrontal cortex
- -> responsible for identifying sounds
Auditory where pathway
Starts in the posterior part of the core + belt
- -> extends into the prefrontal cortex
- -> responsible for locating sounds
Direct sound
Sound reaching the ears directly from where it originated
Indirect sound
Sound reaching the ears from different locations
Precedence effect
We generally perceive sound as coming from its source, rather than from many different directions at once
Reverberation time
The time it takes for a sound to decrease to 1/1000th of its original pressure
–> it this time is too long it may echo, which is difficult to localize
Auditory scene
Array of sound sources at different locations in the environment
Which cues help separating sound sources ?
a) location cue
b) onset time
- -> if 2 sounds start at slightly different times, they’re from diff. locations
c) Pitch + timbre
- -> sounds having same pitch have same location
d) Auditory continuity
e) melody schema
f) pitch proximity
Melody schema
Representation of a familiar melody that is stored in a persons memory
Auditory continuity
Sounds with the same frequency or smoothly changing frequencies are perceived as continuous
–> even when they are interrupted by a different stimulus
Signal transmission from cochlea to the parabelt area
–> Signals are transmitted out of the cochlea toward the auditory receiving area by synapsing in
- cochlear nucleus
- Superior Olivary Nucleus
- Inferior Colliculus
- Medial Geniculate Nucleus
(SONIC MG) - auditory receiving area
–> Signals then travel to
a) core area
b) belt area
c) parabelt area
Auditory scene analysis
Process by which the stimuli produced by each of the sources in the scene are separated
Scale illusion
The idea that if you present tones to each ear that jump up and down you will perceive them as smooth
Harmonicity
Grouping based on harmonical relationships to the fundamental
–> if you’ve a fundamental with harmonics that are close together you are more likely to group them together
Pitch proximity
The hearer tends to link successive tones that are close in pitch and to separate those that are further apart
–> particularly salient when presented at rapid speed
Franssen effect
When a loudspeaker presents a tone of abrupt onset, brief duration and another presents a tone of long duration, the listener will perceive the two tones as a single entity coming from the speaker that produces the abrupt tone
–> incorrect localization of a sound
Conductive hearing loss
Damage to outer or middle ear
–> hearing aid is needed
Sensorineural hearing loss
Damage to hair cells and/or auditory nerves
- -> cochlear implant
- -> auditory stem implant
Hidden hearing loss
Difficulty concentrating on a sound when background noise is present
–> most prevalent in adolescents
