Recently, an implantable hearing aid for rehabilitation of sensorineural hearing loss has been developed. One component of the device is the microphone for implantation into the posterior canal wall. The membrane of the microphone can be covered by skin, cartilage, or fascia, avoiding reduction in sound transmission at the same time. In the study presented here, the microphone was implanted into 50 cadaver specimens of human temporal bone. Localization of the microphone was determined by the anatomical situation of the facial nerve. The microphone and the piezoelectric transducer could be implanted in 78% of the temporal bones after total mastoidectomy. In the final version of the microphone, the size was 4.5 mm and total weight 400 mg.