Auditory Perception week 6
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- Created by: lovelylearner
- Created on: 28-02-22 12:17
Outer Ear
Gather sound
- Pinna
-Tympanic Membrain
- Pinna
-Tympanic Membrain
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Middle Ear
Mechanical transformer
- Ossicles (malleus - incus - stapes)
- Footplate connected to the oval window
- Ossicles (malleus - incus - stapes)
- Footplate connected to the oval window
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Inner ear
where auditory receptors are located
- Semicircular canals
- Vestibule
- Cochlea
- Semicircular canals
- Vestibule
- Cochlea
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How do we capture sounds?
- The middle ear cavity is air-filled while the inner ear is fluid filled.
- The middle ear transfers the force from the tympanic membrane to the oval window through the ossicles.
- The middle ear transfers the force from the tympanic membrane to the oval window through the ossicles.
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Fuction of the inner ear
- High-frequency sounds cause greatest vibration near the base of the membrane and low frequencies cause greatest vibration near the apex.
- The basilar membrane has a frequency-to-place conversion for pure-tone stimuli.
- The basilar membrane has a frequency-to-place conversion for pure-tone stimuli.
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Organ of the Corti
- The inner ear’s receptor organ is the organ of Corti.
-The great majority of afferent axons (to cochlear nucleus) end on inner hair cells. Efferent axons (from superior olivary complex) largely innervate outer hair cells.
- Hair cells are stimulated
-The great majority of afferent axons (to cochlear nucleus) end on inner hair cells. Efferent axons (from superior olivary complex) largely innervate outer hair cells.
- Hair cells are stimulated
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How many hairs does the Corti have in how many rows?
16000 hair cells arrayed in 4 rows: a single raw of inner hair cells and three of outer hair cells.
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Hearing receptors - hair cells
- Hair cells transform mechanical energy into neural signal.
- The deplacement of the stereocilia open K+ channels. This depolarisation open Ca++ channels in the cell’s base, which causes neurotransmitter release to excite afferent axons whose cell bodie
- The deplacement of the stereocilia open K+ channels. This depolarisation open Ca++ channels in the cell’s base, which causes neurotransmitter release to excite afferent axons whose cell bodie
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Function of the inner ear
- The basilar membrane acts like a filter.
- Sounds of different frequency result in maximal displacement at different points along the membrane.
- Sounds of different frequency result in maximal displacement at different points along the membrane.
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Place theory of hearing
- The frequency of a sound is indicated by the place along the cochlea at which the nerve firing is the highest.
- Frequency tuning curves of a cat’s auditory nerve fibers.
The characteristic frequency of each fiber is indicated by the arrow on the x-ax
- Frequency tuning curves of a cat’s auditory nerve fibers.
The characteristic frequency of each fiber is indicated by the arrow on the x-ax
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Cochlear implant
Microphone receiving sound signals from the environment
- Sound processor that divides complex sounds in frequency bands
- Transmitter that sends sound signals
- Array of 22 electrodes implanted along the cochlea.
- Sound processor that divides complex sounds in frequency bands
- Transmitter that sends sound signals
- Array of 22 electrodes implanted along the cochlea.
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The cochlear amplifier
- Effect of outer hair cell damage on frequency tuning curve.
- The outer hair cell cochlear amplifier mechanism occurs when the cells elongate when cilia bend in one direction and contract when the cilia bend in the other direction.
- The outer hair cell cochlear amplifier mechanism occurs when the cells elongate when cilia bend in one direction and contract when the cilia bend in the other direction.
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Sounds localisation : Interaural Time Differences ITD
- Neurons in the Medial Superior Olive (MSO) compute the location of sound by acting as - - - coincidence detectors.
The systematic variation in the delay lengths (delay lines) of the two inputs effectively creates a map of sound location.
- Neuron E w
The systematic variation in the delay lengths (delay lines) of the two inputs effectively creates a map of sound location.
- Neuron E w
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Sounds localisation : Interaural Level differences ILD
- Sounds have higher level intensity at one ear than at the other:
- Head casts an acoustic shadow
- Sound is louder at the ear nearer to the source
(intensity decreases as the inverse-square of the distance)
- Head casts an acoustic shadow
- Sound is louder at the ear nearer to the source
(intensity decreases as the inverse-square of the distance)
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Sound localization
2-Monaural cues
- Pinna showing sound bouncing around in bumps and ridges .
-Frequency spectra recorded by a small microphone inside the listener’s right ear from the same broadband sound coming from two different locations.
- Pinna showing sound bouncing around in bumps and ridges .
-Frequency spectra recorded by a small microphone inside the listener’s right ear from the same broadband sound coming from two different locations.
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Sounds localisation - the vertical plane
Because ears are asymmetrical, much of our ability to localise sound in the vertical plane is due to the shape of the outer ear, in particular the pinna. The pinna provides a monaural cue to sound localisation. The bumps and ridges on the pinna produce re
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Cells of the spiral ganglion project to the Brainstem
The axons of the cells of the spiral ganglion project to the cochlear nucleus and form the auditory nerve.
The nerve fibres are spatially arranged to correspond to their basilar membrane origin. This arrangement is known as tonotopic organisation.
Neuro
The nerve fibres are spatially arranged to correspond to their basilar membrane origin. This arrangement is known as tonotopic organisation.
Neuro
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Coding of information in the higher auditory centers
Tonotopic organisation is maintained in the cortex: the location of active neurons in the auditory neuclei and the cortex is an indication of the frequency of sound.
Two distinct pathways:
‘WHAT’ pathway which is monaural : focuses mainly on identifying
Two distinct pathways:
‘WHAT’ pathway which is monaural : focuses mainly on identifying
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Localisation in area A1 and the auditory belt area
The three main auditory areas in the monkey cortex:
1- the core area which contains the primary auditory receiving area (A1)
2- the Belt area
3- the Parabelt area
P (posterior) A (anterior)
Signals, indicated by the arrows, travel from core to belt and t
1- the core area which contains the primary auditory receiving area (A1)
2- the Belt area
3- the Parabelt area
P (posterior) A (anterior)
Signals, indicated by the arrows, travel from core to belt and t
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basic features of sound waves
Frequency (pitch): nb cycles per second : Hertz (Hz)
Amplitude (loudness): sound pressure level :decibel (dB)
Amplitude (loudness): sound pressure level :decibel (dB)
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Sensitivity to sound - Amplitude
Using the magnitude estimation method, subjects report their perception of loudness in function to the sound’s physical intensity expressed as a proportion of a reference sound intensity (40 dB Sound Pressure Level-SPL).
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Sensitivity to sound - Frequency
The human audible spectrum ranges from 20 to 20,000 Hz (20 KHz).
The sensitivity is greatest in the range of about 500 to 5000 Hz, which includes the range of speech sounds and music.
The sensitivity is greatest in the range of about 500 to 5000 Hz, which includes the range of speech sounds and music.
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Sensitivity to sound - Pitch & Timbre perception
Pitch : The property of auditory sensation in terms of which sounds may be ordered on a musical scale (from low to high). It is most closely related to the physical property of fundamental frequency.
Timber : When two tones have the same loudness, pitch
Timber : When two tones have the same loudness, pitch
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Other cards in this set
Card 2
Front
Middle Ear
Back
Mechanical transformer
- Ossicles (malleus - incus - stapes)
- Footplate connected to the oval window
- Ossicles (malleus - incus - stapes)
- Footplate connected to the oval window
Card 3
Front
Inner ear
Back
Card 4
Front
How do we capture sounds?
Back
Card 5
Front
Fuction of the inner ear
Back
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