An implantable microphone for a hearing prosthesis. The microphone comprises: a housing having a diaphragm chamber formed therein, and an aperture extending from the exterior surface of the housing to the chamber a diaphragm disposed on the exterior of the housing so as to seal the aperture, and configured to vibrate in response to sound signals a sensor positioned adjacent an end of the chamber opposing the diaphragm, and configured to detect vibration of the diaphragm, and to generate electrical signals based thereon and a stiffening material substantially filling the regions of the housing external to the sensor and the diaphragm such that that air gaps within the filled regions of the housing are substantially eliminated, wherein the stiffening material has an elastic modulus that enables the housing to substantially resist deformation there of in response to body-noise.
