And basically, what
happens is summarized on this
diagram. Without going to too much detail,
this is a diagram that really unwinds the
cochlea. And the white spaces you see there
represent the scala vestibule and the scala
tympani. The scala vestibuli starts or commences,
as I mentioned before, at the oval window
in contact with the bony ossicles. The scala
tympani ends at the round window. And right
at the top of the diagram, there's the helicotrema.
That is where the perilymph circulates from
the scala vestibuli to the scala tympani.
So, when the sound waves create the vibration
of the tympanic membrane and that sound energy
is then transferred to mechanical energy through
the bony ossicles, it causes the oval window
to vibrate, and that creates a wave of vibration
through that perilymph. And so the basilar membrane
starts to vibrate. And depending on the frequency
of the sound, it will vibrate at various locations.
It will be displaced. And the maximum displacement
component or location will represent the frequency
of that sound, and there will be different
places for the maximum displacement depending
on the different frequencies of sound, and
that allows us to discriminate sound frequencies.
The basilar membrane detects high frequency
sounds down low at the base of the cochlea.
And rather, low pitch sound or low frequency
sounds up at the apex of the cochlea. At the
apex of the cochlea, the basilar membrane
is its widest, but it's also more relaxed
or less stiff. So this allows different waves
of displacement to be created depending on
the frequency of the sound. And the amplitude
of the sound will change. The amplitude will
create various degrees of displacement.
And that amount of displacement will be the way
in which we can perceive the actual loudness
of the particular sound, not just the frequency.