Physics of hearing
Our ears achieve an extraordinary sensitivity as well as frequency selectivity through tuned mechanical amplification of weak sound signals. The origin of amplification remains, however, enigmatic because of the presence of two distinct mechanical activities in the mechanoreceptive hair cells. We discuss a recently proposed ratchet mechanism in which both active processes together implement unidirectional mechanical amplification. Apart from hearing the mechanism has potential applications in engineering where it may be employed to construct an ultra-sensitive, non-distorting microphone.