The invention provides a smart optical microphone/sensor for sensing distances to a membrane or to a light-reflecting surface, including a source of light for illuminating the membrane or light-reflecting surface; a photodetector for receiving light reflected from the membrane or light-reflecting surface and for producing output signals; adjustable means for supplying power to the source of light, and a pre-amplifier for amplifying the output signals, whereby the sensitivity of the microphone/sensor can be adjusted.