any sound. The background noise would become deafening—not a
good thing! Thus, just as with the rod photoreceptors in the visual
system, the hair cells of the auditory system appear to be operating
with the maximum possible sensitivity given their particular physical
construction.We have considered the process of how, when the energy of a sound
wave hits the head, some of it is funneled into the external ear canal,
then to the middle ear ossicles, then to the cochlea, at which point a
neural signal is generated. Now consider this: there is another way by
which sound energy can reach the inner ear—a different path from
that of the external ear canal route: direct vibration of the bones of the
skull that surround the cochlea. To the extent that the skull is set into
vibration, this will also result in vibration of the tympanic membrane,
ossicles, and cochlea. For most sounds coming from the environment,
this will not contribute much to signals generated in the cochlea.
However, there is one common situation for which the contribution of
skull vibration is very large. Can you guess what that is?