An improved system and method for recognizing an audio signal due to physical activity and taking a predetermined action in response is disclosed. A “reverse noise signal” created by the sound pressure wave of the physical activity acting on the earpiece transducer is obtained. In some embodiments, an ambient noise signal is inverted and fed back, and the inverted signal is added to the intended audio signal being sent to the earpiece so that the ambient noise is cancelled. In other embodiments, a processor receives the ambient noise signal and predicts the modification to the intended audio signal needed to counteract the ambient noise. In other embodiments, the reverse noise signal may represent a motor or biological activity of a user; the system may take different actions in response to different physical activities, such as a heart beat of the user, or a tap, footfall, or swallowing by the user.