An implantable microphone for use with an implantable hearing instrument that has a reduced vibration sensitivity in comparison with its acoustic sensitivity. The microphone utilizes a plurality of small diaphragms as opposed to a single large diaphragm in order to reduce vibration sensitivity caused by mass loading of the diaphragms by overlying skin and tissue. The acoustic outputs of the plurality of small diaphragms are summed (e.g., acoustically or electronically), which allows the microphone to maintain adequate acoustic sensitivity for hearing augmentation purposes while having a reduced vibration sensitivity. In one aspect, the plurality of diaphragms is formed from a single membrane and a multi-apertured support structure in contact with the membrane. Each aperture in combination with the membrane defines a single diaphragm.