Abstract: The bearing accuracy and long-range sonar target detection capability of a multi-cardioid directional receiving hydrophone array is improved by electronically producing mirror images of the cardioid directional patterns of each directional hydrophone in the array whereby the number of receiving channels are effectively doubled by this invention which in turn results in higher signal-to-noise ratios especially when receiving distant relatively weaker sonar signals. As a result, the accuracy of measurement of target range and bearing by the improved directional hydrophone array will be significantly increased.

Abstract: An improved ultrasonic cleaning system employs a plurality of electroacoustic transducers located at different positions on the wall surfaces of a tank containing a cleaning liquid in combination with a source of electrical power and a selective switching system. The switching system applies the electrical power selectively, sequentially and intermittently to any specified one or more of said plurality of electroacoustic transducers to achieve substantially increased cavitation intensity levels in the cleaning liquid and thereby greatly improves the cleaning efficiency of the inventive system as compared to the conventional ultrasonic cleaners which are in widespread use.

Abstract: An improved ultrasonic transducer designed for rugged outdoor applications uses a thin-walled cylindrical tube of polarized ceramic operating in the fundamental circumferential resonant frequency mode. The major portion of the external surface area of the vibrating cylinder is covered by a sound insulating barrier, thereby preventing sound radiation from the covered non-radiating surface area portion of the cylinder. Specific unique relationships between the diameter, length and wall thickness of the ceramic tube, which are necessary to achieve the objects of the invention, are described.

Abstract: The insulation resistance between the electroded surfaces of an underwater transducer and the water within which the transducer is immersed is greatly improved by coating the electroded surface of the transducer with a layer of air-free, high-resistance waterproof material before bonding an elastomer covering over the assembly to serve as the outer housing.

Abstract: A wide-range audio frequency underwater transducer is designed to make use of a massive small diameter vibratile piston driven by electromagnetic oscillatory forces to transmit omnidirectional uniform sound pressure level over the frequency range 100 Hz to 5 kHz. The rugged transducer design is adapted for low-cost mass production and can be used as a highly reliable expendable reference standard of source level for the calibration of in-situ stationary or moving sonar receiving systems. The magnitude of the source level can be accurately controlled by the magnitude of the electrical current supplied to the electrical winding over the entire frequency range of operation. A pressure equalization system is included in the design that permits use of the transducer at any depth down to 500 feet.

Abstract: An electromagnetically driven vibratile piston underwater transducer element generates acoustic intensity levels in excess of 25 peak Watts per square inch of radiating surface in the low audible frequency region within the approximate range 500 to 2500 Hz. The design achieves an efficiency greater than 50% and a very low Q of less than 2. The electromagnetic design employs two separate independent air gaps and a unique mechanical coupling system that combines the electromechanical forces generated in each gap in the proper phase and transmits the combined oscillatory force to drive the vibratile piston.

Abstract: The power handling capacity of a high-power low-frequency underwater transducer including an inertial mass-loaded vibratile piston assembly is greatly increased by increasing the heat conduction from the inertial mass member by designing the vibrating structure to place a surface area portion of the inertial mass member in direct thermal contact with the water environment in which the transducer is submerged. In order to reduce the sound radiation from the exposed surface of the submerged inertial mass member and to obtain a broadband response with a Q equal to 1 or less, a novel rigid hollowed piston construction is described which greatly reduces the weight-to-stiffness ratio of the vibratile plate and achieves the desired low Q as well as a reduction of sound radiation from the exposed inertial mass surface by at least 20 dB below the radiation from the surface of the vibratile plate member.

Abstract: The insulation resistance between the electroded surfaces of an underwater transducer and the water within which the transducer is immersed is greatly improved by coating the electroded surface of the transducer with a layer of air-free, high-resistance waterproof material before bonding an elastomer covering over the assembly to serve as the outer housing.

Abstract: An electromagnetically driven vibratile piston underwater transducer element generates acoustic intensity levels in the order of 50 peak Watts per square inch of radiating surface in the low audible frequency region in the vicinity of 1 kHz. The design achieves an efficiency greater than 50% and a very low Q of less than 2. The air gap is designed to seat mechanically if the unit is operated accidentally at high-power levels while acoustically unloaded thereby protecting the spring assembly from unsafe amplitudes of vibration. The mechanical protective design also serves to protect the transducer vibrating structure from failure if the transducer is exposed to the proximity of an underwater explosive shock wave. The transducer construction results in a minimum overall length so that when the transducer element is mounted in a planar array attached to the hull of a vessel the projection of the radiating surface of the array from the surface of the hull is minimized.

Abstract: A novel configuration of a low-frequency lightweight sonar system is described comprising a coaxial assembly of a transmitting transducer and a directional receiving array contained within a cigar-shaped streamlined cylindrical housing less than 1 ft. diameter which operates in the 3 to 4 kHz frequency region and achieves submarine target detection ranges in the order of 20,000 meters with a bearing accuracy within 2.degree.. The small cylindrical streamlined structural assembly results in a very great reduction in drag resistance while it is being towed underwater at high speeds as compared to conventional sonar domes which must be an order of magnitude larger in diameter to accommodate the larger conventional scanning sonar transducers which are several wavelengths in diameter at the operating frequency.

Abstract: A mechanoacoustic transducer is described which comprises a plurality of circumferentially spaced contiguous vibratile plate members which are driven in phase by a rotating cylindrical cam. The cam is shaped to provide radial oscillatory displacements of the vibratile plates of sufficient amplitude to generate acoustic power density levels in liquids in the order of 100 kW or more per square foot of radiating surface of the cylindrical transducer. The transducer has a diameter of several inches, and it can be lowered into a flooded hole of such size as is usually drilled in an oil field. The mechanically-driven transducer provides an economical means for transmitting very intense low-frequency acoustic power into an oil-bearing shale or sandstone deposit for the purpose of dislodging the trapped oil and increasing the flow rate out of the sediment within which the oil is entrapped.

Abstract: A high efficiency wideband underwater transducer utilizes an axial alignment of transducer elements each employing a thin-walled radially vibrating cylinder mounted coaxially within a 45.degree. conical-shaped reflecting annulus. Each transducer element in the array is made progressively smaller in diameter so that the complete structure takes the shape of a pagoda-like assembly that fits compactly within a small size streamlined waterproof housing.

Abstract: An improved ultrasonic transducer that can be used for cleaning the inner wall surface of water-filled tank, such as a toilet bowl, employs a ceramic disc operating in the planar resonant frequency mode in combination with an acoustic transmission line comprising a solid washer-like annulus bonded to the periphery of the ceramic. The radial dimension of the annulus is made equal to approximately one-half wavelength of sound in the material at the frequency of operation. The annulus serves as an acoustic transmission line to extend the peripheral vibrating surface of the ceramic so that the acoustic power is transferred from the periphery of the ceramic disc to a region closer to the inner wall surface of the tank. The transmission line also increases the radiating area of the transducer element which achieves increased sonic power density in the vicinity of the wall surface.

Abstract: A proximity sensor is mounted on a remote controlled moveable base and is used for detecting a layer of frost of a specified thickness when it accumulates on the subfreezing surface of a refrigeration system. The sensor is positioned at a distance from the subfreezing surface which is greater than the specified thickness of the frost layer which is to be detected. At periodic intervals the moveable base is driven by remote control to move the sensor closer to the subfreezing surface by an amount sufficient for the sensor to make contact with the frost layer when it has accumulated to the specified thickness to be detected.

Abstract: The resonant frequency of an electroacoustic transducer controls the frequency of an oscillating circuit while the transducer vibratile element remains unobstructed. An extended small area portion of the vibratile element is mounted at a fixed distance from the sub-freezing surface of a freezer compartment on which a specified layer of frost is to be detected. When the frost layer builds up to the specified thickness it makes contact with the extended vibratile tip portion of the vibratile element and inhibits the vibration of the vibratile element thus causing the oscillator circuit to stop oscillating. The detected change in the circuit condition is used to initiate the defrost cycle.

Abstract: A test procedure and test apparatus is described for measuring the degradation in the physical integrity of a structural part by measuring the rate of decay of the amplitude of vibration of the part after it has been set into vibration at its free resonant frequency mode. The presence of invisible imperfections in the part such as may occur as a result of metal fatigue or from the development of tiny flaws or cracks will cause an increase in the rate of decay of the amplitude of vibration of the part. By making periodic measurements of the rate of decay of a structural part which is used in a critical highly stressed application subject to vibration such as a jet engine mount, the periodic degradation due to fatigue can be determined and the part is removed from service at a safe period before the degradation reaches an unsafe limit.

Abstract: A mechanoacoustic transducer is described which comprises a plurality of circumferentially spaced contiguous vibratile plate members which are driven in phase by a rotating cylindrical cam. The cam is shaped to provide radial oscillatory displacements of the vibratile plates of sufficient amplitude to generate acoustic power density levels in liquids in the order of 100 kW or more per square foot of radiating surface of the cylindrical transducer. The transducer has a diameter of several inches, and it can be lowered into a flooded hole of such size as is usually drilled in an oil field. The mechanically-driven transducer provides an economical means for transmitting very intense low-frequency acoustic power into an oil-bearing shale or sandstone deposit for the purpose of dislodging the trapped oil and increasing the flow rate out of the sediment within which the oil is entrapped.

Abstract: A portable sonar surveillance system is disclosed which operates in the audible-frequency region where low attenuation loss minimizes the power requirement for achieving long-range detection capability. A light-weight, high-power transmitting transducer array approximately 1 ft. diameter, which operates efficiently in the 4-6 kHz range, is utilized in combination with a novel tri-cardioid hydrophone receiving array whose diameter is only a few inches to achieve a bearing resolution of 5.degree.. The inventive system replaces enormous sized conventional low-frequency scanning sonar systems weighing tens of thousands of pounds. The disclosed system can be very effectively used as a long-range, light-weight "dunking sonar" for submarine surveillance patrol operations from helicopters or small patrol craft.

Abstract: A lightweight high-power transducer employs an axial array of dual-piston transducer element assemblies which are held in concentric alignment within a rigid cylindrical tube by O-rings set into grooves provided in the periphery of the pistons. The pistons have convex shaped vibratile surfaces which, in combination with the sound transmitting fluid which fills the tubular housing, causes each piston to be effectively radiating into an annular shaped tapered horn whose expanding peripheral annular area terminates into a peripheral opening placed in the circumference of the tubular housing. The combination of the inventive transducer with a tricardioid hydrophone results in a lightweight portable sonar system which achieves long-range target detection with a bearing resolution of 5.degree..

Abstract: An electroacoustic transducer which includes a vibratile diaphragm operating at resonance has its narrow band width response characteristic increased by an order of magnitude by the use of a uniquely designed acoustic coupler in combination with the resonant diaphragm. The acoustic resistane presented to the resonant diaphragm by the acoustic coupler dominates the motional impedance characteristic of the transducer in the resonant frequency region of the vibratile diaphragm. The use of the inventive acoustic coupler reduces the Q of the vibrating system from a value in the order of 30 or more to the order of 8 or less.