USA As Represented by Secretary of the Navy

Joseph W Dickey

Lloyd E Powell

Eugene C Fischer

Vincent J Castelli

Jean A Montemarano

Paul M Moore

A composite for use on submarines and surface craft for controlling self-erated noise when listening with sonar. The composite includes two layers of PVF.sub.2 transducers separated by a layer of phase shifting or absorbing material. The inner transducer senses noise from the ship and subtracts this from the signal from the outer transducer representing noise plus the desired signal. In a second mode the sensed noise is regenerated through the outer transducer 180.degree. out of phase to cancel the noise and allow more accurate detection.

Noise control composite

A device for testing hydraulic actuators using acoustical transducers to se sound sources indicative of leaks or other defects in the actuator. A graph of acoustic signals versus piston location may be determined using one acoustic transducer and one position sensor. A correlation function may be obtained by cross-correlating the output from two spaced acoustic transducers.

Acoustical testing of hydraulic actuators

The invention relates to a leak detecting device for pipe systems having electronic channels for processing the acoustical signals from the source of the leak to determine the direction of propagation of the leak signal. Each channel includes a transducer, an amplifier unit, a variable delay unit for delaying the transmission of signals received from the amplifier unit, and a multiple-averager unit which respectively multiplies and then averages input signals from the variable delay unit of the same channel and, depending on the mode of operation, from the amplifier unit of either the same or the other channel. Operating in a first mode to determine the frequency and wavelength of the primary leak signal, the signals from the variable delay unit of one channel are combined with the signals from the amplifier unit of the same channel in the multiplier-averager unit. Upon determining the wavelength of the primary leak signal, the transducers are spaced apart by about one-quarter of such wavelength and attached to the pipe. Operating then in a second mode to determine the direction of propagation of the acoustical leak signal, the multiplier-averager unit of one channel receives signals from the variable delay unit of the same channel and the amplifier unit of the other channel.

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Annapolis, MD, United States of America

Joseph W Dickey