Page 97 - Design in Nature

Communication and Target Location Systems 95

middle ear. The eardrum, 0.30 inch (7.6
millimetre) in diametre, starts vibrating as well.
This vibration is then transferred to the three
bones in the middle ear, where they are
converted into mechanical vibrations that

travel to the inner ear. They then create waves
in a special fluid inside a snail shell-like
structure called the cochlea.
Inside the cochlea, various tones of sound
are distinguished. There are many strings of

varying thickness inside the cochlea just as in
the musical instrument, the harp. The sounds
of the man's friend literally play their
harmonies on this harp. The sound of "greetings" starts from a low pitch and
rises. First, the thicker cords are rattled and then the thinner ones. Finally,
tens of thousands of little bar-shaped objects transfer their vibrations to the

auditory nerve.

Auricle Stirrup Semicircular canals
Anvil Round window
Hammer
Cochlea
Vestibular
nerve
Temporal Bone Oval
window

External auditory
canal

Eardrum Eustachian tube

The auricle is designed to collect and focus sounds into the auditory canal. The inside
surface of the auditory canal is covered with cells and hairs that secrete a thicle waxy
product to protect the ear against external dirt. At the end of the ear canal towards the
start of the middle ear is the eardrum. Beyond the eardrum there are three small bones
called the hammer, anvil and stirrup. The eustachian tube functions to balance air
pressure in the middle ear. At the end of the middle ear is the cochlea that has an
extremely sensitive hearing mechanism and is filled with a special fluid.