There is provided hearing device improvements using modulation techniques adapted to the characteristics of auditory and vestibular hearing. One embodiment provides for extending hearing to the infrasonic range by extracting sounds from the high ambient noise in this range and applying them to a carrier in the ultrasonic quiet zone. Further extension of hearing into the ultrasonic range is provided by a modulation scheme which uses a fluid conduction coupler to match impedance for a vibration transducer applied to the skin. A variation on this embodiment integrates this ultrasonic hearing extension with normal acoustic headphones. Another embodiment compensates for high frequency hearing loss by a modulation scheme which uses middle ear resonance as an amplifier. A further embodiment combines ultrasonic transposition with wireless modulation to obtain secure communication.