Abstract: A hydrophone assembly for deployment on the bottom of a body of water is vided wherein a plurality of hydrophones are mounted in a spaced apart relationship about the circumference of a housing which is designed to hold signal processing electronics. Each hydrophone is constructed to detect a range of frequencies within a defined receive angle that extends outward from the circumference of the housing. A resonance absorbing material is interposed between the housing and the hydrophones to isolate each hydrophone from mechanical resonance. Tilt switches are connected to each hydrophone for automatically and independently selecting hydrophones to participate in the output of the hydrophone assembly based on the orientation of the hydrophones. Selected adjacent hydrophones define a continuous receive angle formed by combining the receive angle associated with each adjacent hydrophone. The continuous receive angle faces upward from the bottom of the water to include an angular portion of the surface.

Abstract: A portable tracking array to be used in a system for determining the track nd/or the range of a target vehicle. The array includes a fiber optic hydrophone for acquiring acoustic signals from the target vehicle. The fiber optic hydrophone is encapsulated within a plastic material such as polyurethane. The array further includes a fiber optic cable for transmitting signals to and for receiving signals from the fiber optic hydrophone, which fiber optic cable has an end encapsulated within a termination coupling, and a length of perforated material extending between the terminal coupling and the plastic material encapsulating the fiber optic hydrophone to allow water entry and to substantially eliminate air cavities which interfere with acoustic performance.

Abstract: A multiplexing node is associated with each analog sensor of a line array. ach multiplexing node has an amplifier/filter section coupled to its associated analog sensor for amplifying and shaping a signal generated by the sensor. An A/D converter then samples the signal. A receiver is coupled to a previous one of the multiplexing nodes for receiving scrambled data and clock information in serial fashion from the previous node. A descrambler is coupled to the receiver to separate the data from the clock. A processor is coupled to the A/D converter and the descrambler. The processor time division multiplexes the data and clock from the previous node with the sampled signal from the A/D converter. The processor scrambles the so multiplexed data, clock and sampled signal. A transmitter is coupled to the processor to transmit the scrambled data, clock and sampled signal in serial fashion over a single data line.

Abstract: A digital calibration circuit provides 1/3 octave center frequencies substially in the range of 50 Hz-12.5 kHz (25 tones) simultaneously at the output at repeatable levels. The system converts digital data to an analog representation for use in calibrating hydrophones. The calibration circuit is comprised of a clock section, a counting section, a clearing section, a data storage/transfer section, and a signal conditioning section. The information that is provided to the output in analog form is stored in digital form in an EPROM within the data storage/transfer section.