Abstract: A hearing assistance device for use with respect to a mastoid cavity and an ear canal with a tympanic membrane, external ear canal bone, incudo-stapedial joint of an ossicular chain and a cochlea having a round window membrane. The device includes a removable unit with a microphone to convert a received sound into electrical sound signals, and includes a digital audio signal processor to process the electrical sound signals into envelopes of the electrical sound signals, and includes an infrared transmitter to transmit the envelopes of sound signals as packages of infrared light pulses. The hearing assistance device also includes an implant unit with a photovoltaic cell to receive the packages of light pulses and demodulate the packages of light pulses into electrical signals, and at least one active electrode that delivers the demodulated electrical signals to the cochlea.