5.1.1. Physical and psychological effects on hearing of exposure to noise

The effect of noise on hearing can be temporary or permanent. Temporary deafness is often experienced after leaving a noisy place. Although hearing recovers within a few hours, this should not be ignored as it is a sign that continued or regular exposure to such noise could cause permanent damage.

Hearing loss is usually gradual due to prolonged exposure to noise. It may only be when damage caused by noise over the years combines with normal hearing loss due to aging that people realize how deaf they have become. Hearing damage can also be caused immediately by sudden, extremely loud noises, though this is not common.

When people are exposed to excessively loud noise, the hearing mechanism itself is damaged. The hearing mechanism transmits noise from the outside environment through the outer and middle ear to the inner ear (the transmission route is ear canal; eardrum; hammer; anvil; stirrup; cochlea). Microscopically small sensory hairs in the inner ear then detect the noise and send nerve impulses to the brain. Exposure to excessively loud noise disturbs these microscopically small hairs.

Sound enters the human ear via the auditory canal and resounds (vibrates) on the eardrum. The vibrations move three small bones: the hammer, anvil and stirrup (malleus, incus and stapes), which cause fluid in the cochlea to move tiny cilia (hair cells). As the cilia move they send electrical signals to the brain, which are interpreted as sound.

Hearing Damage

Exposure to high levels of noise on a daily basis can cause: