The human ear
Ears are a pair of intricate miniaturised organs. This
is so because the various parts of the ear are packed into
a very small space. Ears bring about the sensation of hearing.
What is visible outside is simply a flap of tissue on the
side of the head. This is the outer ear and helps gather
The hearing process consists of the sound vibrations being
converted to signals that can be carried to the brains.
Here they get interpreted and the sound being heard becomes
meaningful. This entire process is carried out in stages
by very intricate inner ear parts that are not visible to
us. The whole process is truly fascinating.
First of all because the inner ear parts are so delicate,
there has to be a mechanism to protect them. Next, there
has to be a mechanism to convert the vibrations that travel
through air, or water or our bones and muscles into signals
that can be sent to the brain for processing. Hence each
part of the inner ear has a very specific task assigned
If you put your finger into your ear, you can feel an opening
at the end. This is actually the beginning of a three-centimetre
long canal that runs obliquely inward. The canal is not
straight because the delicate inner parts of the ear need
to be protected. The non-straight canal makes it difficult
for any object to reach inside. The canal also helps in
warming the air in the ear to keep it cozy. If it gets very
cold inside, as for example during very cold winter days,
you would have experienced a dull pain in your ears. A,
profusion of hairs in the canal and about 4000 wax glands
help in trapping dust and small insects that can cause irritation
in the ears. The wax also guards against infection, particularly
when swimming in dirty water. In short, the inside of the
ear must be clean and dust free. The canal achieves this
Initiator of the hearing process
At the end of the canal is the eardrum. The eardrum is a
tough, tightly stretched membrane less than two centimetres
across. The hearing process starts here. The vibrating air
brought in through the canal strikes the eardrum. Even slight
vibrations caused for example from a whisper can make the
eardrum vibrate. Even if the eardrum is pushed inward by
only about a billionth of a centimeter, it is sufficient
to cause a series of events resulting finally in the sound
Just beyond the eardrum, are three tiny bones hinged together.
These are called the anvil, hammer and Stirrup(also known
as the stapes) because they vaguely resemble those things.
It is their job to amplify the tiny movements of the eardrum.
The tiny bones together amplify the vibrations about 22
times. This should give you a fair idea of how you can hear
whispers and very faint sounds. The anvil is attached to
the eardrum and the stirrup is attached to a thin membrane
called the oval window. The amplified vibrations are passed
on further inside the ear through this membrane.
Beyond the oval window is a fluid filled chamber. The sound
detecting part of the ear is situated here. This is a snail-shaped
cochlea. The interiors of the cochlea are studded with thousands
of microscopic hair like nerve cells. When vibrations reach
here, through the oval window, the fluid in the cochlea
is set into vibrations and the hair like nerve cells are
disturbed. Each nerve cell is sensitive to a particular
vibration and hence to a particular sound. This makes it
possible to distinguish different sounds. The disturbed
nerve cell produces a signal (a tiny amount of electricity),
which is then passed on to the auditory nerve. The auditory
nerve, having a diameter of the order of a pencil leads
into the brain. Thousands of electrical messages (signals)
are passed on to the brain. The brain's job is to unscramble
these data and convert them into meaningful sound.