Have you ever wondered how sounds make their way to our brain? The following is a primer on how we hear.

Our ears are made up of three parts: the outer ear, middle ear, and inner ear (also called the cochlea). All three of these areas work together to detect and process sound.

    1. Outer ear – consists of the pinna, ear canal, and eardrum
      • The pinna collects sound.
      • The ear canal, which is also called the auditory canal, is where sound enters the ear. It connects the outer ear with the eardrum.
      • The eardrum is a thin, cone-shaped flap of tissue that vibrates when sound hits it.
    2. Middle ear– consists of the eardrum, tympanic cavity, and ossicles.
      • The eardrum is also called the tympanic membrane.
      • The tympanic cavity is an air-filled chamber located behind the eardrum.
      • The ossicles are a chain of three tiny bones called the malleus (hammer), incus (anvil), and stapes (stirrup).
    3. Inner ear – consists of the cochlea, vestibular system, and auditory nerve.
      • The cochlea is coiled and looks like a snail, which explains where it gets its name. (‘Cochlea’ means snail in Latin.) It houses thousands of microscopic hairs.
      • The vestibular system helps us keep our balance.
      • The auditory nerve is a bundle of nerve fibers that transmit signals from the inner ear to the brain.

The video below from the National Institute on Deafness and Other Communication Disorders provides a fascinating view of the hearing process and describes how we hear from the origin of the sound to its arrival in the brain.

There are basically five steps in the hearing process.

  1. Sounds waves enter the outer ear through the pinna and travel through the auditory canal to your eardrum.
  2. When the sound waves hit the eardrum, it vibrates. These vibrations are sent to the three small bones that make up the ossicles in the middle ear.
  3. The ossicles amplify the vibrations from the eardrum and send them to the cochlea, the snail-shaped, fluid-filled structure in the inner ear.
  4. Once the vibrations reach the cochlea, the movement of the fluid causes tiny hair cells (called stereocilia) to move. The movement of these hair cells creates electric signals.
  5. The electric signals are moved to the brain by the auditory nerve. The brain then interprets these signals and converts them into information that we can understand.