Abstract: An ultrasonic transmitter generates a reference signal based on a clock signal of a specific frequency and a control signal made up of binary values 0 and 1 for controlling how the level (High or Low) of a carrier drive signal should change, and generates an analog signal constituting the carrier drive signal by pulse-duration-modulating the reference signal. Produced from the carrier drive signal, a driving pulse signal is shaped into a curved waveform having a gradually rising leading edge and a gradually falling trailing edge as the amplitude of the carrier drive signal is gradually increased and decreased based on the control signal.

Abstract: A method is disclosed of generating a predetermined field of cavitation around a remote target in an underwater environment. The method includes the steps of identifying a remote target location, generating at least two acoustic beams, each at a high power output, from an underwater acoustic source, and controlling the generated acoustic beams to intersect with each other at the remote target location and thereby create a destructive cavitation field at the intersection of the beams. The acoustic source and target can be located in unconfined underwater space and at a distance of at least 100 m apart.

Abstract: Provided is a sonar transmitter in which the structure is simplified and the power loss is decreased. A sonar transmitter comprises: a load unit having a transformer constituted with a primary wiring and a secondary wiring, and a wave transmitter to which the secondary voltage generated in the secondary wiring is applied; a control unit for outputting a PWM signal which originally has no offset voltage; and a transmission circuit unit which amplifies the PWM signal outputted from the control unit and applies it to the primary wiring as the primary voltage. The control unit comprises a memory circuit formed by ROM or RAM which stores a transmission signal waveform and a control circuit formed by a microcomputer or DSP, for example. With the present invention, a conventional feedback circuit, an adder and the like become unnecessary by outputting the PWM which originally contains no offset voltage.

Abstract: The present invention discloses an ultrasonic and infrared transmitter with tunable carrier frequency, which comprises an oscillation frequency, a frequency divider, a multiplexer and an output buffer on an integrated circuit in association with an infrared light emitting diode or ultrasonic transducer to transmit infrared or ultrasonic carrier signals. The oscillation frequency is divided by the frequency divider and sent to one input of the multiplexer which has the other input connected with a user-controlled data, and finally the output buffer outputs the data. The integrated circuit provides two carrier signal output ports, and the carrier signals from these two output ports are inverted to each other, thus the described apparatus can transmit not only infrared carrier signal but also ultrasonic carrier signal.

Abstract: An acoustic wave sensor utilizes one or more acoustic waves trapped in an acoustic wave cavity to detect the presence of one or more substances on a surface of the acoustic wave cavity. To detect the presence of ice, a trapped torsional acoustic wave is used. To detect water, an acoustic wave with flexural or compressional components is used. The sensor includes a number of transducers adjacent the acoustic wave cavity where a controller drives different sets of the transducers to generate different acoustic waves.

Abstract: An acoustic logging tool includes external baffle assemblies forming a waveguide structure at the acoustic source. The logging tool is designed for acoustic logging of earth formation surrounding a borehole. The external baffle assemblies form a waveguide structure that is designed to increase signal to noise ratio in an acoustic logging tool using dipole or other acoustic waves. In a preferred embodiment, the acoustic logging tool includes an elongated transmitter module, and a receiver sonde having a linear array of acoustic receivers. The transmitter module includes first and second cylindrical masses spaced apart along the axis by first and second spacers. The first cylindrical mass defines a first circular facing surface and a first cylindrical outer surface. The second cylindrical mass defines a second circular facing surface and a second cylindrical outer surface.

Abstract: A circuit for driving an electromagnetic source for generating acoustic waves has a dischargeable high-voltage capacitor with a diode or a diode module connected in parallel therewith.

Abstract: An ultrasonic coding modem for digital network communication comprises a transmitting device having a first piezoelectric substrate, and a receiving device having a second piezoelectric substrate. If a message digital-signal is applied to the transmitting device, a SAW is excited on the first piezoelectric substrate and is delivered as a coded digital signal into a digital network. On the other hand, if the coded digital-signal is received at the receiving device from the digital network, a SAW is excited on the second piezoelectric substrate. In this time, if the SAW excited on the second piezoelectric substrate is corresponding to the SAW excited on the first piezoelectric substrate, an output digital-signal, which is equivalent to the message digital-signal, is delivered from the receiving device. As a result, it is possible to keep a base-band communication secret.

Abstract: A parametric sonar for use in a liquid medium includes a first signal generator which transmits a first acoustic signal and a second signal generator transmitting a second acoustic signal which interatct to produce a difference frequency signal at an interference region. A cavitation generator is provided to transmit a cavitation acoustic wave causing cavitation vapor bubbles in the liquid medium at the interference region. The cavitation vapor bubbles improve the efficiency of generating the difference frequency signal.

Abstract: An acoustic device that places existing components in a damping pattern after transmitting an acoustic signal. In one embodiment, the device comprises a transistor bridge and an acoustic transducer. The transistor bridge is coupled between two predetermined voltages having a voltage difference, and the acoustic transducer is coupled between the arms of the transistor bridge. The transistor bridge enters a damping configuration after applying an excitation pattern to the acoustic transducer. In the damping configuration, the input terminals of the transistor bridge are preferably grounded. In applying the excitation pattern, the transistor bridge preferably applies the voltage difference to the acoustic transducer in alternate polarities. In a preferred embodiment, the acoustic transducer includes a transformer having a primary winding coupled between the arms of the transistor bridge, and further includes a piezoelectric crystal coupled to a secondary winding of the transformer.

Abstract: Presented is a device for transmitting data, for storage and use, to small electronic devices without need for additional devices being incorporated into one the communicating devices. Data is transmitted from a second device a to a first small electronic device. In transmitting the data, the second electronic device encodes the electronic data for sonic transmission. This is done by preparing a sound generating file that then drives the speaker of the second electronic device. A microphone of the first electronic device receives the sound waves/frequencies and then decrypts them into digital form. In a less preferred embodiment, the first electronic device may also encrypt electronic information for sound generation to drive the speaker of the first electronic device. Then, the microphone of the second electronic device receives the sound and decrypts it into its digital form and stores the decrypted information into a memory location.

Abstract: The present invention relates to an electroacoustic transducer where the voltage of a capacitive acoustic element is controlled by charging and discharging the charge of the element via an inductance (L) by fast switches (K1, K2). In the case energy unconverted into the acoustic energy of the transducer can be transferred to an energy storage of an electrical circuit formed by the inductance (L) and the capacitance (C1, C2, C0) during each control sequence and in this way the transducer can be made to operate with a good coefficient of efficiency.

Abstract: An arbitrary waveform generator includes an arithmetic element that can access samples from a waveform sample memory and adjust values accessed from the waveform sample memory to modify waveform power or amplitude. In an illustrative embodiment of the arbitrary waveform generator, the arithmetic element is a multiplying digital-to-analog converter (DAC) that has a first input connection for receiving digitized waveform samples and has a second input connection for receiving a reference signal. An output signal from the multiplying DAC is a mathematical product of the digitized waveform samples and the reference signal. In one example, a reference digital-to-analog converter (DAC) generates the reference signal. In some examples, the digitized waveform samples are digitized samples of an analog waveform signal. In some examples, the arithmetic element is incorporated into the arbitrary waveform generator in a manner to maintain transmit signal resolution over a full range of transmit power settings.

Abstract: A low frequency sound generator is depicted in FIG. 1, having a resonator tube with an open end and a closed end, with a pulsing mechanism for admitting puffs of compressed gas into the closed end for purposes of producing sound waves out of the open end. The pulsing mechanism resides inside, and is movable along the axis of the resonator tube at the closed end, providing the means of closure for said resonator tube. The axial position of the pulsing mechanism is set through adjusting means, and determines the effective length of the resonator tube, thereby controlling the resonant frequency of the emitted sound.

Abstract: Sonar method and system for determining and using beamform factors for forming sonar beams approximating an optimum sonar beam for the directional transmission or reception of sonar energy by a sonar phased array system. Optimum maximum and minimum dependent beamform factors are determined from initial beamform factors and an initial parent population of chromosomes is generated, each chromosome including a gene corresponding to a dependent beamform factor and representing an initial candidate beam. Subsequent parent populations are generated by chromosome cloning. A child population is generated from a parent population by exchanging statistically selected pairs of genes and generating a mutated population. A surviving population is selected from the mutated population by a chromosomes comparison. When the surviving population chromosomes meet the criteria, the best match genes of the surviving population are selected for forming a beam.

Abstract: A device for influencing human behavior comprises an audio system arranged to produce a sound wave that may be directed to a selected location and a video system arranged to produce a light beam that may be directed to the selected location. The audio system preferably comprises a frame and an array of sound generators mounted in the frame; The frame preferably is formed generally as a tube having a longitudinal axis, an open end and a closed end with the sound wave being emitted generally parallel to the longitudinal axis of the tube. The video system preferably comprises either a flash tube or a laser.

Abstract: An ultrasonic transmitting and receiving system for digital communication comprises; a transmitting device including a first piezoelectric substrate, an input IDT, a first electrode-group, and an envelope detecting device; and a receiving device including a second piezoelectric substrate, an output IDT, a second electrode-group, an intermediary IDT, and an output IDT. Two neighbors of interdigital electrode pairs of the input IDT are at a distance L from each other. The first electrode-group consists of interdigital electrodes A0 and A1, at a distance L from each other. The second electrode-group consists of a central interdigital electrode B0, a left interdigital electrode B−1 at a distance L0 from the electrode B0, and a right interdigital electrode B1 at a distance L0+L from the electrode B0. The input- and output IDTs have coded patterns in reverse to each other.

Abstract: Arrangement and method for controlling audio reception by occupants of a vehicle in which the position of any occupants is determined and the entertainment system controlled to provide specific sound for the occupants based on the determined positions of the occupants. Sound generating components of the entertainment system are automatically adjustable based on the determined position of the occupants. A hypersonic sound generating system may be used wherein ultrasonic frequency generators generate ultrasonic waves which mix with ultrasonic waves generated by another ultrasonic frequency generator to thereby cause the creation of new audio frequencies in an area determined based on the position of the occupants. In addition, the presence and direction of unwanted noise may be detected and sound created to cancel the unwanted noise in the area including the determined positions of any occupants.

Abstract: In the method according to the invention, several adjacent synchronized ultrasonic sensors automatically generate a clock signal with measurement clocks (M1, M2, M3). The transmission pulses (S1, S2, S3) of three ultrasonic sensors are generated with changing transmission pulse offset (d1, d2, d3) with respect to the respective measurement clocks (M1, M2, M3). Thereby, extrinsic echo signals of adjacent ultrasonic sensors can be masked out since only these echo signals change their position relative to the transmission pulses (S1, S2, S3). In contrast, the actual sought echo signal does not change its respective position relative to the transmission pulse (S1, S2, S3).

Abstract: The invention pertains a bathymetric sonar system involving a single swept transmit beam projector system which compensates for ship attitude and positioning changes. A sonar transducer array has a matrix of acoustic projector elements arranged in a plurality of substantially parallel rows and a plurality of substantially parallel columns; and means for causing each of the projector elements to generate an acoustic signal at a frequency and phase independently from each other projector element. Preferably the transducer array is operated by causing the projector elements to generate an acoustic signal at a frequency and phase independently from each other projector element, at a frequency and phase which is initially the same as the frequency and phase of each other element in its column and such that the frequency and phase of the projector elements in each column is different from each other column. Thus a single swept beam is projected toward the ocean floor.

Abstract: A sound generating apparatus or a sound detecting apparatus includes: a flexible substrate; and a plurality of bimorphs arranged on a surface of the flexible substrate in a direction at a predetermined interval, each of the bimorphs having input/output terminals. Each of the bimorphs has a rectangular shape and its longitudinal direction is perpendicular to the direction. The flexible substrate has a slit between successive two of the bimorphs. A width of the slit outside the bimorphs is wide. A buffering material covering surfaces of the flexible substrate with the bimorphs exposed or a cover covering the bimorphs with a space may be provided. The cover and the buffering material may have slit. A sound generating apparatus including a plurality of flexible substrates respectively supporting bimorphs may be provided. The flexible substrate may have a comb shape.

Abstract: The invention integrates an amplifier directly into an electromechanical transducer assembly. In one embodiment of this invention, power from a power supply is supplied to what can be described as an electromechanical amplifier that includes bridge circuits that directly drive the transducer elements. Each transducer element can include its own co-located switching network, such as, for example, a bridge circuit, that can be used with other system components to control when and for how long a voltage of equal magnitude and of either a positive or negative polarity is selectively directed to the element to expand or contract it in relation to a signal desired to be acoustically transmitted. Besides permitting an output of two voltages of equal magnitude and opposite polarity, the bridge circuit also permits an output that is “open” and one that allows a dissipation of transducer element charge.

Abstract: An ultrasound transmitting circuit includes an electrical transmitter from which electrical oscillations can be fed at an electrical transmission power level over a connecting line into an ultrasound transducer. The electrical oscillations are formed of a current signal and a voltage signal. The ultrasound transducer can be excited by the electrical oscillations to produce ultrasound oscillations. In order to allow ultrasound oscillation power to be controlled more accurately, the current signal and the voltage signal can be supplied to a phase regulator. A variable impedance, which is coupled to the connecting line, can be actuated by the phase regulator in such a manner that the current signal and the voltage signal are in phase.

Abstract: A power envelope shaping device for joining to a serial control output is sclosed. Multiple power switcher modules are joined to a plurality of incremental power sources and controlled by the power select circuitry module. In this way, each power switcher module can provide power from at least one of the incremental power sources on command from said power select circuitry module. The power switcher module outputs are joined together in order for providing varying power levels in accordance with a preprogrammed power envelope shape.

Abstract: An ultrasonic sound source broadcasts an ultrasonic signal which is amplitude and/or frequency modulated with an information input signal originating from an information input source. If the signals are amplitude modulated, a square root function of the information input signal is produced prior to modulation. The modulated signal, which may be amplified, is then broadcast via a projector unit, whereupon an individual or group of individuals located in the broadcast region detect the audible sound.

Abstract: An optoacoustic system comprises an optoacoustic transducer including a first array of acoustic transducers and a second array of optical fibers; an acoustic subsystem for controllably exciting at least a first subset of the acoustic transducers to generate acoustic pulses with a prescribed pulse width, and for forming a first image based on return acoustic pulses reflected from a patient; an optical subsystem for controllably generating optical pulses to be transmitted through at least a first subset of the optical fibers toward the patient, and for forming a second image based on light reflected from the patient; and image correlation means for correlating the first and second images. The first and second arrays may take various forms, including the form of an annular array in which the acoustic transducers are arranged coaxially and the optical fibers are disposed around an outer periphery of the first array. The first and second arrays may also take the form of linear arrays.

Abstract: A rugged ultrasonic sensor is provided which is capable of detecting objects in very close proximity to the sensor. This close proximity detection includes the detection of objects which are immediately adjacent the sensor housing. Such close range operation is achieved by tailoring the transducer to operate at previously undesirable conditions, including low Q and high frequency. Such operating conditions allow the resonating characteristics of the transducer not to interfere with close range operation.

Abstract: A very low frequency augmentation system consists of a mobile target very w frequency projector (VLFP) adapted for operation as an augmentation device and installed within a torpedo shell housing. The housing is loaded within the torpedo tube of a submarine. A control and power interface is provided between the housing and the submarine to operate and monitor the augmentation device from the submarine. The housing is loaded in one of the submarine's torpedo tubes and the tube is flooded. The VLFP transmits low frequency vibrations into the surrounding seawater, acting as an augmentor.

Abstract: An acoustic array transducer capable of forming narrow dispersion, broadband or narrowband acoustic beam sets in two dimensions with a minimum aperture size. Concurrent yet independent electrical interfacing with array transducer elements allows simultaneous formation of multiple transmit and receive beams inclined within two planar orientations normal to the array face, while requiring a minimum amount of supporting circuitry. A method of economically and accurately fabricating the aforementioned transducer array by incrementally dicing bonded layers of solid discs of transducer materials being rigidly held together is also disclosed.

Abstract: A system for ultrasound transmission in materials comprising a reference unit, an examination unit, at least a case equipped in at least the examination unit, and a signal processing unit. The reference unit consists of at least an input ultrasonic transducer T.sub.o and at least an output ultrasonic transducer R.sub.o. The examination unit consists of at least an input ultrasonic transducer T.sub.s and at least an output ultrasonic transducer R.sub.s. The case is placed between the ultrasonic transducers T.sub.s and R.sub.s. The signal processing unit is connected with output terminals of the ultrasonic transducers R.sub.o and R.sub.s. When electric signals are applied to the ultrasonic transducers T.sub.o and T.sub.s, ultrasounds are emitted in air from the ultrasonic transducers T.sub.o and T.sub.s, respectively, and then received by the ultrasonic transducers R.sub.o and R.sub.s, respectively.

Abstract: There is disclosed a digital frequency synthesizer which converts an ultrnic burst from an echo-ranging sonar system into a continuous signal having a frequency exactly equal to the frequency of the cycles making up the burst. This burst is detected and a number representing the period of this burst generated and transmitted to a first counter. A clock pulse train is generated and transmitted to a second counter. When the numbers in the first and second counters coincide, a single output pulse is generated and the second counter reset. When this cycle is repeated, the frequency of the resultant pulse train reflects any change in frequency of the cycles making up the bursts.

Abstract: Methods, apparatuses, and devices are disclosed for collecting a veil including long fibers with high speed conveyor surfaces to produce a web of loosely related fibers, and further forming a wool pack by distributing the web of fibers with low frequency sound. The methods, apparatuses, and devices are particularly useful in collecting long fibers, and producing wool packs including long glass fibers.

Abstract: A low power transmitter providing selectable waveforms includes a self-coined power source, such as a battery. A timer powered by the battery provides a transmitter actuation signal after a predetermined delay. A voltage regulator coupled to the power source and to the timer provides power in response to the transmitter actuation signal. A waveform generator coupled to the voltage regulator provides one or more selected continuous or pulse waveforms when power is supplied by the voltage regulator. The waveform generator is pre-programmed with one or more selected continuous or pulse waveforms in digital format. The waveform generator outputs at least one selected waveform selected when power is provided by the voltage regulator. Any waveform may be selected by appropriately programming the waveform generator.

Abstract: A method of alerting marine mammals and other mammals underwater to the danger of approaching motor vessels includes generating a pulsed acoustical signal at a predetermined source frequency and at a fixed or variable (with boat speed) sound pressure level and projecting the generated signal underwater in a highly directional manner from a motor vessel and in a direction corresponding with the direction of travel of the motor vessel or from fixed hazards which present a danger to mammals underwater; the projected pulsed acoustical signal having an underwater frequency ranging between 3 kHz and 26 kHz.

Abstract: An ultrasonic active impedance matching device between an ultrasonic transducer and a generator of pulses includes an interface stage (100) and a matching stage (200) which are connected by way of a coaxial cable (150) having an impedance of 50 ohms. The interface stage (100) has a sub-assembly (10, 11, 12, 13, 14) for generating a d.c. signal having an amplitude which is proportional to but smaller than the peak value of the pulses, a sub-assembly (15, 16, 17 50) for generating a low-voltage pulse which is matched with the impedance of the cable, and a programmable power supply (18) for producing a d.c. voltage which is applied to the transducer via the cable. The matching stage (200) has a sub-assembly (19) for transmitting the excitation pulse of the transducer (2) and a receiving sub-assembly (20, 21) for returning the echographic signal to the generator (1) via the cable (150).

Abstract: The identity of an aquatic organism is determined by a signature derived from a broadband acoustic signal transmitted and received by a broadband transducer or transmitted by a an broadband acoustic transmitter and received by an array of broadband acoustic receivers. The signature is a set of classifier coefficients created from a training processing that learns to discriminate between various size/taxa of aquatic life forms using features extracted from the received broadband echoes. The signature database used for classification during operation is stored on a portable storage medium. The degree to which the signals collected from an unknown aquatic life form matches the predefined known aquatic life form is then reported to a utilizing device.

Abstract: The invention provides a controlling device which comprises a control box, a power box, a right sensor control unit attached to a plurality of proximity detectors, a left sensor control unit attached to a plurality of proximity detectors, and a valve box control unit, wherein each proximity detector comprises an ultrasonic transducer, a first circuit for handshaking, noise reduction and voltage regulation, and a second and third circuit for digital signal generation, analog reception and digital conversion, wherein the first circuit is connected between a left or right sensor control and second and third circuits of a proximity detector.

Abstract: A sonar transducer includes an electro-mechanical transducer coupled to a front mass and a back mass. Annular rings space a compliant diaphragm from the front mass, the diaphragm being in communication with the liquid to which the sonar transducer is exposed. The compliance of the diaphragm is selected to tune the sonar transducer to eliminate reactive components of the impedance of the combined sonar transducer and liquid medium load, and to maximize the radiation resistance of the system.

Abstract: Improvements on the Parra "METHOD AND APPARATUS FOR SEPARATING DOLPHIN FROM TUNA" using the primordial fear of dolphin of killer whales to separate dolphin from tuna wherein the sound of feeding killer whale is recorded, digitized, edited and enhanced to produce digitally synthesized killer whale sounds. These digitally synthesized sounds of one or more feeding killer whale is played under water and in the vicinity of a mixed school of dolphin and tuna and as the dolphin leave said vicinity, catching the tuna in nets. According to the present invention, one or more of a plurality of playback units are selectively triggered on and off from a remote location to steer the dolphin to safety. The playback unit is carried in an elongated hollow tube having a weighted end and a recovery end, the weight causing the end it is on to go to a predetermined depth in the sea with the recovery end having a hook for aerial retrieval.

Abstract: An ultrasonic unipolar pulse/echo instrument uses active switches and a timing and drive circuitry to control electrical energy to a transducer, the discharging of the transducer, and the opening of an electrical pathway to the receiving circuitry for the returning echoes. The active switches utilize MOSFET devices along with decoupling circuitry to insure the preservation of the unipolar nature of the pulses, insure fast transition times, and maintain broad band width and time resolution. A housing contains the various circuitry and switches and allows connection to a power supply and a movable ultrasonic transducer. The circuitry maintains low impedance input to the transducer during transmitting cycles, and high impedance between the transducer and the receiving circuit during receive cycles to maintain the unipolar pulse shape. A unipolar pulse is valuable for nondestructive evaluation, a prime use for the present instrument.

Abstract: A dive profile recorder for monitoring conditions encountered by a diver under water includes a plurality of transducers to be carried by a diver for generating electrical signals representative of the conditions encountered by the diver. Encoding circuitry electrically connected to the transducers encodes the electrical signals to form a serial data stream and a transmitter electrically connected to the encoding circuitry transmits the serial data stream through the water. A receiver remote from the diver receives the transmitted serial data stream and decoding circuitry electrically connected to the receiver decodes the serial data stream to electrical signals representative of the conditions encountered by the diver. A display electrically connected to the decoding circuitry receives the electrical signals and displays human-perceptible indicia of the conditions encountered by the diver in response to the received electrical signals.

Abstract: Pulsed ultrasonic apparatus for monitoring a swimming pool includes a transmitter housing securable to a child and provides a swept frequency pulsed output from a transducer within the housing when an electrical circuit is completed by having a pair of tabs on the outside of the housing immersed in water. The output from the transducer is detected by a receiving hydrophone and the hydrophone is connected to receiver circuitry which provides an appropriate alarm signal.

Abstract: An ultrasonic transmission-reception system having a piezoelectric transducer for at least transmitting ultrasonic waves, a current generator for exciting the transducer so that it transmits an ultrasonic wave and electronic processing means able to determine in an approximate manner and store at least one current generator exciting signal. The exciting signal being associated with a reference object and leads to a predetermined detected ultrasonic wave shape from said object following the interaction of said object with the ultrasonic wave produced by the transducer as a result of the excitation of the current generator.

Abstract: An expendable moving echo radiator suitable for providing a decoy to attr a homing torpedo and divert the torpedo away from its intended target is disclosed. The present invention provides an expandable and collapsible curtain for deployment from a capsule launched from a submarine or other sea vessel. In its expanded configuration, the curtain is characterized by a physical profile sufficient to reflect acoustic waves and to generate echoes substantially similar to echo signals generated by an actual, full size submarine or other target. The present invention is further provided with propulsion means, as well as means for enhancing its capability to capture a torpedo's sensors. It can also be provided with explosives to destroy lured torpedoes. The expendable device can be used to simulate a submarine for anti-submarine warfare (ASW) training, thereby affording the advantage that a package of easily transportable size becomes a full size submarine-like target.

Abstract: A remote-control system for closures with a movable hand transmitter with at least one transmission key, this transmitter generating and radiating directed coded control signals upon actuation of the transmission key of the hand transmitter. At least one first receiver unit is tuned to receive the control signals radiated from the hand transmitter and is arranged on a motor vehicle and triggers switching effects on a remotely controllable vehicle locking after the received control signals have been identified as acceptable. At least one second receiver unit is tuned to receive control signals radiated as a result of the actuation of the transmission key of the hand transmitter for remotely controlling a remotely controllable access control device external to the motor vehicle. This second receiver unit is arranged outside the motor vehicle and triggers switching effects on the access control device after the received control signals have been identified as acceptable.

Abstract: An active adaptive noise canceller that inserts delays in the weight update logic of an adaptive filter employed by the canceller to make the filter stable. It has been found that there is a great deal of flexibility regarding the selection of the delay values. This insensitivity permits designing the delays in advance, and not having to adjust them to different situations as they change, thus no longer requiring a training mode. The canceller dramatically reduces the amount of hardward needed to perform active adaptive noise cancelling, and eliminates the need for the training mode, which in some applications, including automobiles, for example, can be as objectionable as the noise sources that are to be suppressed.

Abstract: A driver circuit for an acoustic transducer includes a voltage regulator that provides a regulated DC output level for a high value load impedance and when the load impedance falls to a low value, its DC output exhibits a substantially reduced level. A transformer is connected between the voltage regulator and the acoustic transducer. A switching circuit is connected to the transformer and is responsive to a leading edge of a pulse input signal to reflect a low value impedance through the transformer to the voltage regulator. The switching circuit is further responsive to a lagging edge of a pulse input signal to reflect a high value impedance to the voltage regulator. A capacitive reactance circuit is coupled to the transformer and is responsive to the switching circuit reflecting a low value impedance to manifest a reduced charge state.

Abstract: Linear and switching amplifiers associated with acoustic transducers requ a gradual turn-on rather than an abrupt full-power level signal. A transducer preamplifier power controller circuit prevents the operation of fuses and the tripping of circuit breakers when the relatively high power driving levels for a sonar transducer are initiated. The controller circuit gradually increases a signal level from a zero level to a maximum during the initiation of a sonar signal using a threshold level that is set to a fraction of the expected maximum, and two discrete clock frequencies, for example at 1 MHz and 2 KHz actuate interconnected digital control elements incrementally to increase the signal level during a predetermined period. This cycle is re-initiated by the next sonar signal.

Abstract: A method of establishing an ultrasonic standing wave in a fluid medium is described in which the standing wave is produced by an acoustic energy output along a path extending through the fluid medium, the frequency of said energy output being changed cyclically while maintaining an essentially constant mean frequency. The cyclic frequency change sweeps said energy output frequency between upper and lower limits that represent a difference of at least one half-wavelength at the mean acoustic frequency over the length of said path, so that a fully resonant standing wave appears in each cycle, regardless of transient ambient variations. For stability, the cycle time of the sweep is maintained substantially greater than the travel time of the acoustic energy output over the length of the path.

Abstract: A visualizing method for three dimensional standing wave sound field comprises the steps of mixing into a liquid medium a large number of fine particles of the same density as said liquid medium and exposing the liquid medium containing the fine particles to a three dimensional standing wave sound field produced by ultrasonic waves thus causing the fine particles to move to positions where the amplitude of the sound pressure is minimum, the sound pressure distribution of the three dimensional standing wave sound field being visualized by the distribution of the fine particles.