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What is the auditory system? (BRAIN (Auditory nerve, 2. cochlear nucleus =…
What is the auditory system?
SOUND
= pressure changes, hearing something
pure tones
(=tones composed by 1
fundamental frequency
= lowest frequency of sound) and
complex tones
(= multiple pure tones)
amplitude/intensity
= difference from highest and lowest pressure area --> loudness (measured in Decibels)
Frequency/pitch
= how many times there's a pressure change in one second --> pitch (measured in Hertz)
EAR STRUCTURE:
OUTER EAR:
Pinna
= outer part of ear for localization of sounds
Auditory canal
= canal for protection of tympanic membrane and enhancement of sounds
Tympanic membrane
= sheet of skin for vibration
Eustachian tube
= for keeping pressure in middle ear same as in outer ear
MIDDLE EAR
Ossicles
= malleus, incus, stapes. for passing vibration and amplifying it
Oval window
= membrane for passing vibrations to inner ear
INNER EAR
Cochlea
= "snail" structure for trandusction (=transformation of sound waves to neural signals)
tympanic canal
= canal where vibrations descending
Vestibular canal
= canal in which vibrations ascending
Middle canal
= canal in between tympanic and vestibular
reissner membrane
= wall of middle canal
Basilar membrane
= support of organ of corti and related to hair cells
Tectorial membrane
= vibrating with sound and moving hair cells
Organ of cort
i = sitting on basilar membrane and below tectorial. For transduction. Composed by
hair cells
= cells enabling transduction.
Round window
= membrane separating cochlea and middle ear. for pressure changes.
Auditory nerve
= for transmitting signals from hair cells to other structures
SOUND PATH
1.wave of sound to tympanic membrane
ossicles and oval window
cochlear with vibration of fluids
vibration of membranes
deflection of
cilia
= kind of bristles on hair cells
firing to auditory nerve
Place theory
= understand frequency of sound according to place where sound wave stops in cochlea
Place theory
= understand frequency of sound according to place where
sound travelling wave
stops in cochlea
Envelope of travelling wave
= maximum displacement of travelling wave
Proof of place theory -->
masking experiment
= hearing sound gradually covered by another sound
Audibility threshold
= minimum audible sound
Characteristic frequency
= minimum frequency necessary to increase neurons' firing rate
Results of experiment: sounds are covered more by other sounds with same frequency --> higher audibility threshold
BRAIN
Auditory nerve
2.
cochlear nucleus
= structure in brain stem
3.
superior olive
= for convergence of info from both ears
4.
inferior colliculus
= where info crosses
5. medial geniculate nucleus
= structure with mainly efferent neurons from brain
6.
primary auditory cortex
= A1
7.
Secondary auditory cortex
= belt and parabelt for higher processing
Tonotopic organization of neurons
= neurons organization according to the frequencies they respond to
HEARING LOSS
Conductive hearing loss
= sound not getting to receptors
Sensorineural hearing loss
= damage to hair cells and brain
Presbycusis
= old hearing. Because of age
Noise-induced hearing loss
= damage to hair cells because of loud noises
Otosclerosis
= abnormal growth in middle ear bones
Hyperacusis
= hypersensitivity to certain sound frequencies
SOUND LOCATION
Auditory space
= space where you can localize an object
Three dimensions for location (
azimuth
- left right,
elevation
- up down,
distance
of sound from listener)
Location cues
= cues to determine location of sounds
Binaural cues
= cues from both ears and for azimuth.
Interaural time difference
= time difference between hearing sound in left ear and in right ear. For detecting low frequency sounds
Interaural level difference
= difference in sound pressure level. For location of high frequency sounds
Monaural cues
= cues from one eye. For elevation.
spectral cue
= where sound moves in pinna --> elevation of sound
Narrowly and broadly ITD neuro
ns = neurons for sound location
GESTALT PRINCIPLES OF AUDITORY GROUPING
Location (sounds from same area put together
Pitch and timbre = sounds with same pitch and timbre put together -->
auditory stream segregation
(= differentiation of sounds according to pitches and timbres)
Proximity in time --> sounds from same source
Auditory continuity = continuous sounds from same source
Experience
