An apparatus includes at least one housing configured to be implanted within a body of a recipient, at least one acoustic transducer positioned on or within the at least one housing, at least one motion sensor positioned on or within the at least one housing, gain circuitry configured to apply a gain to transducer output signals from the at least one acoustic transducer, at least one storage device, and at least one processor operatively coupled to the at least one acoustic transducer, the at least one motion sensor, the gain circuitry, and the at least one storage device. The at least one processor is configured to adjust the gain circuitry in response to a reference acoustic sensitivity function, a reference vibration response function, the transducer output signals, and sensor output signals from the at least one motion sensor.