hearing process

2. The ear is our organ of hearing. It is divided
into three parts: outer, middle, and inner.
The outer ear is shaped like a funnel and is
called the pinna or auricle. It is that part of
the ear at the side of our head. The pinna
receives sound waves that travel auditory
canal or ear canal. The auditory canal acts
like a tunnel with an approximate length of
2.5 cm and leads to the eardrum. The ear
canal also protects the eardrum from shock
and external objects.

3.  The middle ear is an air-filled space
containing the eardrum or tympanic
membrane, the Eustachian tube, and
the bridge of ossicles. The eardrum is a
cone-shaped piece of skin about 10 mm
wide. It is very sensitive. Even the
slightest pressure variation will cause it
to vibrate. The eardrum separates the
outer ear from the middle ear. The
ossicles are the smallest bones in our
body. These three bones are named
according to their shapes : the malleus
(or hammer), incus (or anvi), and stapes
(or stirrup). The bridge is arranged in the
following sequence: malleus, incus, and
stapes. The maleus is connected to the
eardrum, while stapes are attached to
the oval window. The inner ear contains
a coiled, fluid-filled tube called the
cochlea. Suspended the cochlea is the
basilar membrane ends of hair cells
linking organ of the audtory nerve called
the organ of Cort.

4.  The pinna collects sound waves and transmits
them to the auditory canal. The auditory canal
acts like a closed tube amplifier that produces a
resonant frequency with a wavelength equal to
four times its length. This resonant frequency is
about 3 400 HZ. This partly explains why
human ear is very sensitive to frequencies in
the range of 300 Hz to 4000 Hz.
 Sounds travels through the eardrum. The
pressure variation resulting from the
compresions and rare fractions n the sound
wave causes the eardrum to vibrate.