These are the actual sensory receptors of the inner ear. These cells are equipped with tiny cilia on their surface. Sounds that are perceived by the external ear and the middle ear causes these tiny cilia to move, which will set in motion  a series of reactions that will transform the mechanical signal into an electrical signal. The electrical signal will then make its way to the brain via the auditory nerve.

Once the cilia are damaged or destroyed from exposure to loud noise the signal can no longer be transformed, and the sound will not be heard. Unfortunately, these ciliated cells cannot be replaced. Their destruction is permanent as is the hearing loss that ensues.

At birth we possess approximately 15000 ciliated cells  that correspond with our auditory potential. There are different factors that can damage these cells such as, noise, aging, certain medications, chemical products in addition to genetic factors.