Hyperacusis is the condition of heightened sensitivity to sound often to the point that normal, everyday noises are painful. This is often the result of damage to the structures of the inner ear. Although the exact mechanism of this problem is not well understood, it is believed that the efferent fibers of the inner ear are damaged while the hair cells that allow the hearing of pure tones remain intact. Efferent inner ear fibers originate in the brain and serve to regulate hearing. Somewhat rarer is hyperacusis that can be defined as a cerebral processing problem specific to how the brain perceives sound. Least common is vestibular hyperacusis, a difficulty of the vestibular system that causes the brain to perceive some tones as motion as well as sound.