Hair cells and tinnitus

In the cochlea, there is a flexible membrane, that is some 33 mm long and moves due to sound. The same is true for the about 16,000 hair cells that are organized in four rows – one row of internal hair cells and three rows of external hair cells. Each cell specializes in particular sound frequencies, and each of them have 20-300 affixed sensory hairs. When a sound is registered, the cells send 30,000 nerve signals to the brain.

If the small, fine hair cells in the cochlea are harmed, such as by loud noise, it could cause tinnitus. When the hairs have been harmed, they send error signals to the brain about sounds, typically a constant beep, even though there is no such external sound source. The damage to the hair cells is irreversible, so tinnitus cannot be cured. However, the condition can be treated in different ways, by which the brain is typically distracted by other sounds, so the inconvenience is minimised. Thousands of cochlea sensory hairs move like seaweeds on the ocean floor, picking up sound.