A device to transmit sound to an ear of a user, the ear comprising a middle ear and an eardrum, the device comprising: an output transducer assembly configured to couple to a tissue of a middle ear of a user, the output transducer assembly comprising at least one transducer configured to receive energy transmitted through the eardrum; and a sound transducer coupled to the at least one transducer and configured to transmit the sound to the user in response to the energy when the output transducer assembly is supported with the tissue of the middle ear of the user, the sound transducer having a diaphragm configured to vibrate and displace air to transmit the sound to the user in response to the energy, characterized in that: the at least one transducer is configured to receive light energy comprising at least one of ultraviolet light, visible light, or infrared light transmitted through the eardrum, wherein a portion of the output transducer assembly comprises an extension sized to fit within a round window niche to couple to the round window with air with the air extending between the sound transducer and the round window, the extension comprising a channel having a maximum cross sectional dimension of no more than about 3 mm to fit within the round window niche and concentrate sound pressure, the channel extending from the diaphragm of the sound transducer to an opening, the opening positioned on the extension to orient toward the round window when the assembly is supported with the tissue of the middle ear channel, wherein the diaphragm is configured to vibrate and displace air to transmit the sound to the user in response to the light energy, and wherein the sound transducer is configured to transmit low frequency sound comprising first frequencies below about 4kHz to the user via the eardrum and to transmit high frequency sound comprising second frequencies above about 5kHz to the user via the round window, the device having a sound processor with circuitry adjusted so as to compensate for different gains amongst the frequencies, based on the transfer function of the relative coupling of the eardrum and the round window to the sound transducer. an output transducer assembly configured to couple to a tissue of a middle ear of a user, the output transducer assembly comprising at least one transducer configured to receive energy transmitted through the eardrum; and a sound transducer coupled to the at least one transducer and configured to transmit the sound to the user in response to the energy when the output transducer assembly is supported with the tissue of the middle ear of the user, the sound transducer having a diaphragm configured to vibrate and displace air to transmit the sound to the user in response to the energy, the at least one transducer is configured to receive light energy comprising at least one of ultraviolet light, visible light, or infrared light transmitted through the eardrum, wherein a portion of the output transducer assembly comprises an extension sized to fit within a round window niche to couple to the round window with air with the air extending between the sound transducer and the round window, the extension comprising a channel having a maximum cross sectional dimension of no more than about 3 mm to fit within the round window niche and concentrate sound pressure, the channel extending from the diaphragm of the sound transducer to an opening, the opening positioned on the extension to orient toward the round window when the assembly is supported with the tissue of the middle ear channel, wherein the diaphragm is configured to vibrate and displace air to transmit the sound to the user in response to the light energy, and wherein the sound transducer is configured to transmit low frequency sound comprising first frequencies below about 4kHz to the user via the eardrum and to transmit high frequency sound comprising second frequencies above about 5kHz to the user via the round window, the device having a sound processor with circuitry adjusted so as to compensate for different gains amongst the frequencies, based on the transfer function of the relative coupling of the eardrum and the round window to the sound transducer.