Auditory System. Auditory System. Adequate Stimulus for the auditory system is sound. What is sound? Two components of sound displacement component movement of molecules pressure component alternating compression and rarefaction. Human ears are sensitive only to the
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Adequate Stimulus for the
auditory system is sound
What is sound?
Two components of sound
movement of molecules
alternating compression and rarefaction
Human ears are sensitive only to the
pressure component, and only between
20 Hz and 20 kHz
Pinna or auricle
Auditory canal or ear canal
Tympanic membrane or eardrum
Malleus or hammer
Incus or anvil
Stapes or stirrup
vestibuli shown in red; scala media in dark blue.
Scala tympani and scala vestibuli are filled with perilymph; scala media is filled with endolymph.
Viewed in cross section, the cochlea contains three small parallel chambers. These chambers, the scalae, are separated by Reissner’s membrane and the basilar membrane. The organ of Corti contains the auditory receptors; it sits upon the basilar membrane and is covered by the tectorial membrane.
a.k.a. cochlear ganglion
The spiral ganglion so named because the cell bodies follow the spiral path of the bony cochlea around the modiolus.
It is also known as the cochlear ganglion.
Place theory: Pitch perception based on PLACE of greatest displacement of basilar membrane and thus, WHICH spiral ganglion cells are most active.
Rate theory: Pitch perception based on the
RATE of action potentials in spiral ganglion cells.
Therefore, maximum difference in time of arrival at the two ears is
.2 m/335 m/sec, or about 6 msec.
wavelength is less than the size of the object
casting the shadow, intensity differences are
useful when wavelengths are less than
the I.D. (~.2 m; frequency greater than
~ 1,700 Hz).
Differences in time of arrival at the two ears
Is unambiguous only when wavelengths are
greater than 1/2 the I.D. (~.1 m; frequency less
than about 3,400 Hz).
from the pinna.
1. Intensity differences: high frequencies
2. Interaural delay: sudden onset
and low frequencies
3. Spectral cues: effect of reflection by pinna
on sound spectrum
Because sounds are complex, consisting of
many frequencies, all three mechanisms are
typically used simultaneously.
to a Sound Source
1. Sound intensity
Spherical spreading of sound energy
2. Spectral properties
Atmospheric attenuation of high frequencies
Greater number of echoes with distance
250 500 1000 2000 3000 4000 6000 8000
The macula of the saccule is oriented vertically.