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Lemieux / Allenbach-Bellehumeur Audioprosthetists

Hearing and the Ear

Fig1. - Anato-physiology of Hearing.

The ear can be divided in 4 parts.

Outer ear

The outer (external) ear includes the pinna and the external ear canal. The pinna directs the sound to the ear canal. The external ear canal is dotted with hairs and has glands that produce earwax. Earwax helps to lubricate the skin, to keep it moist and to protect against infections.

Middle ear

The eardrum (tympanic membrane) is a membrane at the inner end of the external auditory canal which vibrates when sound is received. The ossicular chain (malleus, incus, and stapes) amplifies and transmits these vibrations to the inner ear.

Inner ear

The inner ear has two parts: one is responsible for hearing, and the other part is involved in the equilibrium function . The auditory part includes the cochlea and the auditory nerve. The cochlea is snail-shaped and is filled with liquid in which hair cells move. When the ossicular chain transmits a vibration to the hair cells, it creates an electrical signal.

Central auditory system

The central auditory system is made of nerve cells and some areas of the brain. It is responsible for the recognition of sound, the understanding of speech in noise and the analysis of complex sounds, such as music. Hearing impairment in the central auditory system may lead to a central auditory processing disorder (CAPD).

The first signs of hearing loss

  • I hear, but I don’t understand clearly what people say.
  • I often ask people to repeat.
  • The TV or radio as to be louder for me to understand clearly.
  • It’s harder to understand conversation in a group or in background noise.
  • I feel like people are mumbling, their voice isn’t clear.
  • It’s hard to identify where sounds are coming from.

The main causes of hearing loss

  • Wearing out of the inner ear, related to the aging process of the human body
  • Exposure to loud noises (noisy workplace, loud music, gunshots…)
  • Infection
  • Injury to the head, neck or ear
  • Medication that can be toxic for the ear (chemotherapy, some antibiotics)

Hearing versus Understanding

It is important to differentiate hearing and understanding. A hearing-impaired person will hear sounds, speech, noises. But she will have a hard time to understand clearly, especially if many people are talking at the same time, or in background noise.