An intrinsic frequency limit to the cochlear amplifier

The cochlear amplifier in the inner ear determines hearing in mammals. The amplifier consists of senorimotor cells, outer hair cells, which change the passive mechanics of the cochlea. It is thought that the molecular basis of the mechanism is a voltage-sensitive motor protein. The limiting frequency at which the motor operates is shown to lie near 25 kHz, setting an upper limited to the hearing range in mammalian cochleas.