Hearing

Hearing is one of the senses, allowing organisms to perceive sound. Sound is fundamentally a wave of vibrations travelling through air, water, or solid matter. The ear converts these waves into nerve signals, which the brain then interprets.

Hearing is measured by two properties: sound intensity (loudness), measured in decibels (dB), and wavelength or vibration frequency, measured in hertz (Hz). People with typical hearing generally perceive sounds in the range of about 20 Hz to 20,000 Hz, though the upper limit decreases with age.

Parts of the ear

The ear has three sections. The outer ear (the auricle and ear canal) collects sound and directs it to the eardrum. The middle ear contains three small bones that amplify vibrations and transmit them onward. The inner ear houses the cochlea, a fluid-filled spiral structure where hair cells convert vibrations into electrical signals.

How the brain processes sound

Signals from the cochlea travel along the auditory nerve to the sound-processing regions of the brain. The brain compares the timing and intensity of sound reaching both ears, allowing a person to locate the direction from which sound has come.

Changes in hearing

Hearing can diminish for various reasons: age, prolonged exposure to loud sound, infection, certain medications, or congenital conditions. When hair cells are damaged, they typically do not regrow. Hearing aids and cochlear implants are available to support hearing.