How Does the Human Ear Work?

Ear is a major organ of the auditory system that helps in detecting and perceiving sound waves. It may be used to define the visible portion (pinna or auricle) or the entire organ. The position of ear (two on opposite sides of the head) and the parts contribute to localizing and perception of sound.

The outer ear is the first receiver of sound waves. It consists of the ear flap and ear canal (2 cm long). The middle ear, as the name suggests, lies between the outer and inner ear. It is basically an air-filled cavity (tympanic cavity). It is connected to the mouth via the Eustachian tube and helps in balancing pressure.

The middle ear is separated from the outer ear by the eardrum, and consists of three tiny bones, viz., hammer (malleus), anvil (incus), and stirrup (stapes). After this comes the inner ear, which is made up of a cochlea (spiral tube), semicircular canals, and the auditory nerve. Any damage in any of the ear parts may result in different problems.

The ear parts function in coordination for sensing, collecting, and interpreting the sound waves. Each component is responsible for carrying out specific functions. The external or outer ear collects sound waves and channelizes them to the middle ear.

In this process, the ear flap first receives the sound waves, transfers them to the eardrum (tympanic membrane) via the ear canal (meatus). The length of the ear canal also contributes in amplifying the sound. Sweat glands secrete earwax in the canal.

If the earwax is produced in excessive amount, then it hampers the hearing ability of the individual. It can also lead to infections and at times even hearing loss.

The sound waves that are collected by the outer ear remain as pressure waves until they reach the eardrum. The eardrum is a flexible membrane that vibrates after receiving the pressure waves.

As the sound waves reach the eardrum, the three tiny bones, or auditory ossicles, vibrate in response to the sound waves and convert the sound energy into a compressional wave. The middle ear is connected with the inner ear by the stirrup bone.

It is by the transmission of vibrations by the stirrup bone into the inner ear that the compressional wave is created. The main function of the auditory ossicles is to amplify the sound.

The inner ear components, namely, the cochlea and the semicircular canals, are fluid-filled structures. In the inner lining of the cochlea, there are over 20,000 minute nerve cells which differ in length and resiliency. As soon as the compressional wave reaches these nerve cells, they resonate at certain frequencies and release an electrical impulse.

This impulse is perceived by the auditory nerve and transmitted to the brain. In the brain, the impulses are interpreted as sound. Thus, the human ear is a complex structure that performs important functions like hearing, head positioning, and/or maintaining the balance.