An inner ear cell, called an outer hair cell, rockin’ around the clock!
Since the amplitude, and hence the mechanical energy, of airborne sounds is tiny, the cochlea mechanically amplifies the incoming vibrations. The motors which supply this mechanical amplification are the outer hair cells. Like inner hair cells, they use stretch receptors associated with the stereocilia at their tips to sense vibrations and convert them to electrical neural signals. But only in outer hair cells are these currents used to control length changes which parallel, and effectively amplify, the incoming mechanical vibration.