HEARING PROCESS

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.

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.

The Physics of Hearing 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.

Reported by:Bridgette Yutuc