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Sound in the Brain - Coggle Diagram
Sound in the Brain
sound
physical
pressure change
condensation - increase in pressure
rarefaction - decrease in pressure
sound waves
pure tones - sine waves
frequency
amplitude
complex tones
first harmonic - fundamental frequency
higher harmonics - integer multiples of the fundamental frequency
perceptual
pitch
fundamental frequency
tone chroma - octaves
effect of the missing fundamental - e.g. phone conversations
loudness
audibility curve - different perceptual thresholds for different frequencies
figure
timbre
attack and decay
harmonic structure of a tone
periodic vs aperiodic sounds
from pressure change to electrical signals
figure anatomy
vibration is transmitted through outer and middle ear to inner ear
outer ear
pinnae
auditory canal
increasing sound pressure level of frequencies between 1000 and 5000 Hz through resonance - most sensitive range of human hearing
tympanic membrane (eardrum)
middle ear
ossicles
amplifying pressure - necessary because of transfer from air to water
malleus
incus
stapes
oval window
inner ear
cochlea
figure
hair cells in the organ of corti - receptors for hearing
cilia bend in response to pressure change
transduction
cilia bend in one direction, ion channels open
cilia bend in other direction, ion channels close
alternating bursts of electrical signals
release of neurotransmitters at synapse between inner hair cells and auditory nerve, causing auditory nerve to fire
phase locking
firing at peak of the sine wave
Fourier analysis
tonotopic organisation
pitch perception
place
temporal information
even if fundamental frequency is absent, repetition rate remains the same
phase locking
temporal coding major mechanism of pitch perception?
(subcortical) pathway to the cortex
(cochlea)
cochlear nucleus
superior olivary nucleus (brainstem)
locating sounds - signals from left and right ear meet here first
inferior colliculus (midbrain)
medial geniculate nucleus (thalamus)
primary auditory cortex (A1)
SONIC MG