Miracle Behind Human Ear

Although some animals can hear sound frequencies beyond the range of human hearing,
the combination of a human's ears and brain is affordable one, say audio experts.
Our hearing enables us to determine loudness,pitch,and tone and to approximate the
direction and distance of a sound source. The frequency range of a healthy human ear is
roughly 20 to 20000 hertz,or cycles of sound oscillation per second. The most sensitive
region is in the 1000 to 5000 hertz range. Moreover, we may be able to detect a change of just
one hertz from,say,440 hertz to 441 hertz.
Indeed, a healthy ear is so sensitive that it can detect sounds when the vibration ,or
to and fro movement,of the air at the eardrum is less than the diameter of an atom. According
to a university course on hearing,"the human hearing system is close to the theoretical
physical limits of sensitivity. There would be little point in being much more sensitive to
sound,as all we would hear would be a 'hiss,'" the result of the random movement of the atoms
and molecules that make up the air.
Eardrum vibrations are amplified mechanically by lever action and are transferred to the inner
ear by means of the ossicles-tiny bones known as the hammer,the anvil,and the stapes. But what
if your ears are suddenly struck by a deafening sound? In that event, they have a built-in
protective mechanism in the form of muscle action that adjusts the ossicles to reduce the force of
the sound. However, the ears are not equipped to deal with prolonged loud noise