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: 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 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: An acoustic alarm repeater system detects a coded alarm signal such as might be produced by a smoke detector or burglar alarm. The alarm signal can vary over a wide dynamic range since the signal will usually be greatly attenuated by intervening walls or floors. The system includes an electroacoustic transducer for converting the coded audible alarm signal into an electrical signal; an amplifier; and an autocorrelator for recognizing the presence of the repetitive characteristic of the coded acoustic alarm signal. Upon detecting the presence of the coded alarm signal, the system generates a new loud warning signal. The processing system may be designed to detect a wide variety of differently coded alarm signals. A dual repeater system recognizes the presence of two differently coded alarm signals, such as one produced by a smoke detector and the other produced by an intrusion alarm, and responds differently to each.

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.

Abstract: The resonance frequency of an electroacoustic transducer is precisely and quickly adjusted by the continuous removal of material from the vibratile surface while the resonance frequency is continuously monitored. The material removal rate is electronically controlled and is automatically decreased as the resonance frequency of the transducer approaches close to the desired specified value. The removal of material is automatically stopped at the precise instant when the adjusted resonance frequency becomes equal to the desired specified value.

Abstract: An improved sound ranging system increases the precision of range measurement by automatically correcting for any variation in the velocity of sound in the medium. The automatic correction for the sound velocity utilizes a small sound reflecting target located at a precise fixed distance from the transducer surface. A digital circuit, including a microcomputer, improves the measurement accuracy of the system. The invention includes a time delay and sensitivity control in one of the two time measurement circuits employed in the system to prevent "ghost" signals caused by multiple round-trip target reflections from introducing errors in the range measurements.

Abstract: A fixed array of three identical directional receivers, each having a carid directional pattern, are arranged in a symmetrical configuration with each receiver having its principal axis of maximum sensitivity oriented 120.degree. from the corresponding axes of its neighbors. By comparing the relative magnitudes of the voltages generated in each of the three cardioid receivers upon receiving a signal, the bearing of the signal source is automatically determined and displayed. The tri-cardioid receiving array overcomes the prior art need for large-sized directional receiving transducers, and also overcomes the need for mechanically rotating or electronically scanning the receiving array to find the bearing of the signal source.

Abstract: An improved method of manufacturing electroacoustic transducers which emp vibratile transducer elements includes an automatic method of measuring the motional impedance vs. frequency characteristics of a plurality of transducer elements and an automatic method of segregating the transducer elements into separate groups which are selected in accordance with the similarities of the measured motional impedance characteristics of the elements. The separate groups of selected transducer elements are then processed by changing a mechanical dimension of the elements in each separate group by a different specified amount which adjusts the motional impedance vs. frequency characteristic of each separate group to the same specified desired value. The processed transducer elements are then assembled into complete transducers, thereby achieving improved uniformity in the performance characteristics of the transducers which is obtained at relatively low cost.

Abstract: An improved transducer utilizes an acoustic delay line to adjust the phase f the acoustic output from the out-of-phase portion of a free resonant flexural disc so that it is constructively added to the acoustic output generated from the remaining portion of the resonant flexural disc. The improved transducer combines an acoustic coupler with the housing structure of the transducer for the purpose of increasing the radiation resistance load on the vibratile disc to achieve increased acoustic output from the transducer.

Abstract: An improved transducer utilizes an acoustic delay line to reverse the phase f the sound vibrations generated by the peripheral area of a bi-laminar vibratile disc operating at its free fundamental resonance mode. When the diameter of the vibratile disc is dimensioned within specific limits in comparison with the wavelength of sound being radiated at the frequency of operation, the radiation efficiency of the transducer is significantly increased over the efficiency of the same vibratile disc operating in the prior art manner with an acoustic shield placed over the peripheral area of the disc to prevent destructive interference from the out-of-phase sound radiation generated by the peripheral area.

Abstract: An intrusion alarm system includes a microcomputer and keyboard for providing control functions for the alarm system with greater reliability and with greatly increased security as compared with prior art systems. The disclosed system provides a positive means for deactivating the alarm system only by authorized personnel by the use of a multi-digit code which must be correctly entered on the keyboard within a prescribed short period of time after entry into the protected zone. Upon entry into the protected zone, the system goes immediately into a preliminary alarm stage which, for example, may be the lighting of a floor lamp in the room. The person entering the premises then has thirty seconds to enter the correct code on the keyboard attached to the front panel of the alarm unit to deactivate the system.