How does noise-induced hearing loss happen?
Noise-induced hearing loss (NIHL) takes place gradually and is often unnoticed until it reaches a certain level. It results from damage to the outer hair cells of the cochlea. The outer hair cells amplify low-level sounds that enter the cochlea. Damage to the inner hair cells that actually convert the sound waves to electrical signals and transmit them to the brain is very rare. Damage to the outer hair cells and the associated hearing loss is irreversible. Current estimates indicate noise-induced hearing loss affects from 10 to 15 million people in United States. The figures below show the location of the cochlea and the outer hair cells of the ear.
