A passive vibration cancellation system manufactured of a plurality of waterproof diaphragms and a more rigid support structure is sized to cover a microphone of an auditory prosthesis. The system includes multiple flexible diaphragms that deform in opposite directions when acted upon by sound, but deform in the same direction when acted upon by vibrations. The system can further include a collar or other compliant element to help secure a microphone assembly into the auditory prosthesis housing, while further reducing vibration transmission between the housing and the microphone.