Abstract: Apparatus for enhancing human hearing includes a pair of parallel-connected directional microphone elements responsive to frequencies ranging from below the audible frequency range to above the audible frequency range, the microphone elements facing in opposite directions and mounted in a parabolic reflector. The microphone element output signals are separated into infrasonic, sonic, and ultrasonic channels by filters. The infrasonic and ultrasonic channel signals are processed by a frequency heterodyning process to signals having frequencies within the range of human hearing. The channel signals are then selectively combined, amplified, and supplied to an earphone to render audible sounds outside the range of human hearing and aid in the detection, location, and classification of events of interest.