Abstract: A single test transducer or a line array of test transducers is placed above the transducers of an array under test and provided with a simulated flow noise signal. The response of all of the transducers under test is derived and stored whereupon the test transducer or line array of test transducers is moved to a subsequent position wherein the process is repeated. After all positions are indexed, the stored signals representing the outputs of all of the transducers of the array under test for all transmissions are combined and processed to derive a transducer array output signal for analysis purposes.

Abstract: A cylindrical transducer for use as a low frequency hydrophone and having inner and outer electrodes at least one of which is deposited in a certain predetermined pattern having smooth continuous lines whereby the electrode coverage varies as a function of transducer axial length.

Abstract: A transducer made up of a plurality of piezoceramic tubes arranged in end to end relationship with elastomeric material between tubes. The tubes are poled and driven axially; however, the hoop mode of operation is utilized to obtain a fan-shaped beam extremely narrow in one direction and extremely broad in the direction perpendicular thereto. A suitable backing arrangement is provided for the transducer when mounted on a support body to prevent degradation of the beam pattern.

Abstract: A solid state transmit-receive switching element having multiple resonant rcuits connected in a bridge arrangement by back-to-back zener diodes. While receiving, the zener diodes have a high impedance and the bridge arrangement acts as two series tuned circuits in parallel. While transmitting, the zener diodes breakdown and the bridge arrangement appears electrically as two parallel tuned circuits in series.

Abstract: A sand transport detector which detects the discrete impingements of sand particles on an elongated probe member inserted into the sand. A piezoelectric transducer element is cemented to the probe and produces an output signal when impingement occurs. With an electronic circuit coupled to the transducer, an indication of sand transport may be obtained.

Abstract: An energy imaging system providing high resolution at the center of the field of view and reduced resolution as a function of the distance away from the center.