Abstract: Ultrasonic signals are used to transmit sounds from a modulated ultrasonic generator to other locations from which the sounds appear to emanate. In particular, an ultrasonic carrier is modulated with an audio signal and demodulated on passage through the atmosphere. The carrier frequencies are substantially higher than those of prior systems, e.g., at least 60 kHz, and the modulation products thus have frequencies which are well above the audible range of humans; as a result, these signals are likely harmless to individuals who are within the ultrasonic fields of the system. The signals may be steered to moving locations, and various measures are taken to minimize distortion and maximize efficiency.

Abstract: An integrated single channel or multi-channel ultrasound transmitter that minimizes the number of input connections to a controller such as an FPGA, field programmable gate array, or a custom integrated circuit in an ultrasound system. The method is accomplished by integrating, in low voltage logic, a means to store and or program the patterns required for the transmitter output. The number of logic input connections can be further reduced by further integrating, in low voltage logic, programmable individual time delays and frequency divider for each transmitter output.

Abstract: Arrangement and method for obtaining information about a vehicle occupant in a compartment of the vehicle in which a light source is mounted in the vehicle, structured light is projected into an area of interest in the compartment, rays of light forming the structured light originating from the light source, reflected light is detected at an image sensor at a position different than the position from which the structured light is projected, and the reflected light is analyzed relative to the projected structured light to obtain information about the area of interest. The structured light is designed to appear as if it comes from a source of light (virtual or actual) which is at a position different than the position of the image sensor.

Abstract: An ultrasonic system including an ultrasonic transmitter and an ultrasonic receiver is provided. The ultrasonic transmitter emits a transmission signal, which includes a synchronous burst and multiple data bursts. The ultrasonic receiver receives a synchronous echo, and determines whether the amplitude of the synchronous echo is larger than a first threshold. If the amplitude of the synchronous echo is larger than the first threshold, then the ultrasonic receiver interprets the multiple data echoes corresponding to the data bursts to obtain a digital signal.

Abstract: Fullerenes, when irradiated with electromagnetic radiation, generate acoustic waves. A photoacoustic tomography method using a material comprising fullerenes is disclosed that includes irradiating the material with a radiation beam such as a laser. The resultant photoacoustic effect produced by the material is detected by at least one detector. A photoacoustic tomography system using a material comprising fullerenes is also described.

Abstract: A monopole acoustic transmitter for logging-while-drilling comprising as a ring that comprises one or more piezoelectric arc segments. The ring is oriented in a plane whose normal is essentially coincident with the major axis of a logging tool in which it is disposed. The ring disposed within a recess on the outer surface of a short, cylindrical insert. The insert is inserted into a drill collar, rather than into the wall of the collar. The ring can comprise a continuous ring of piezoelectric material, or alternately arc segments or active ring segments of piezoelectric ceramic bonded to segments of other materials such as alumina to increase the frequency or heavy metals such as tungsten to reduce the frequency. The material and dimensions of the material used in-between the piezoelectric segments is chosen to alter the frequency of the ring.

Abstract: An apparatus and method are provided for transferring data through a submarine hull or other solid boundary using high frequency acoustic signals, so avoiding penetration of the hull or boundary. First and second transducers are mounted on opposed surfaces of the hull and aligned to communicate acoustic signals through the hull. The first transducer is driven by a continuous wave carrier signal modulated with data. A demodulator detects that data in the modulated acoustic signals received by the second transducer. Critically, the dimensions of the first and second transducers and the frequency of the carrier signal are selected so as to reduce the interference by triple transit signals through the hull to a level sufficiently low to enable continuous communication of data through the hull at a bit rate of at least 1 MHz. Carrier signals of the order of 40 MHz may be used to achieve data bit rates of the order of 15-18 MHz through the hull.

Abstract: A signal decay time adjusting method is used in an ultrasonic transducer. Firstly, a first driving signal is generated by a pre-processing module. When the first driving signal is received, an ultrasonic transmitting/receiving module generates vibration and transmits a sensing wave according to the first driving signal. Then, the pre-processing module stops generating the first driving signal so that the vibration generated within the ultrasonic transmitting/receiving module is decayed as a decay signal. Then, a second driving signal is generated by the pre-processing module according to the first driving signal, and the second driving signal is transmitted to the ultrasonic transmitting/receiving module. When the second driving signal is received, the decay signal is offset according to the second driving signal, so that a decay time of the decay signal is shortened. When the sensing wave is reflected by an object, a reflective wave is received by the ultrasonic transmitting/receiving module.

Abstract: The present invention discloses an ultrasonic apparatus with an adjustable horn. The ultrasonic apparatus comprises a transmission device, a horn and an ultrasonic transceiver device. The horn and the transmission device are geared by a helical gear. The ultrasonic transceiver device is connected to the end of the helical gear. When the transmission device moves the horn to a first position, the ultrasonic transceiver device is applied for on/off control; while the transmission device moves the horn to a second position, the ultrasonic sensor is applied for digital control.

Abstract: Electronic devices and accessories such as headsets for electronic devices are provided. A microphone may be included in an accessory to capture sound for an associated electronic device. Buttons and other user interfaces may be included in the accessories. An accessory may have an audio plug that connects to a mating audio jack in an electronic device, thereby establishing a wired communications link between the accessory and the electronic device. The electronic device may include power supply circuitry for applying bias voltages to the accessory. The bias voltages may bias a microphone and may adjust settings in the accessory such as settings related to operating modes. User input information may be conveyed between the accessory and the electronic device using ultrasonic tone transmission. The electronic device may also gather input from the accessory using a voltage detector coupled to lines in the communications path.

Abstract: A measurement system for capturing a transit time, phase, or frequency of energy waves propagating through a propagation medium is disclosed. The measurement system comprises two different closed-loop feedback paths. The first path includes a driver circuit (628), a transducer (604), a propagation medium (602), a transducer (606), and a zero-crossing receiver (640). The zero-crossing receiver (640) detects transition states of propagated energy waves in the propagation medium including the transition of each energy wave through a mid-point of a symmetrical or cyclical waveform. A second path includes the driver circuit (1228), a transducer (1204), a propagation medium (1202), a reflecting surface (1206), and an edge-detect receiver (1240). Energy waves in the propagating medium (1202) are reflected at least once. The edge-detect receiver (1240) detects a wave front of an energy wave. Each positive closed-loop path maintains the emission, propagation, and detection of energy waves in the propagation medium.

Abstract: A system and method for forming acoustic beams is disclosed. One embodiment is an acoustic system configured to generate a plurality of beams non-orthogonal to a transducer array simultaneously with a vertical acoustic beam orthogonal to the array. The acoustic system includes a plurality of transducer elements arranged to form a two-dimensional array and electrically connected into rows in a first dimension and columns in a second dimension.

Abstract: The disclosed system uses seismic signaling to locate survivors in a mine collapse. A separate transmitter with a specific pre-selected frequency or frequencies is placed in pre-positioned safety zones of a mine. The system generates frequency-locked, unmodulated seismic energy, which allows rescuers to identify the safety zone where a transmitter is activated. The transmitter comprises an oscillator that generates the signal. The oscillator drives the transducer. The transducer causes the inertial mass to move. The movement of the inertial mass generates the seismic waves, which are conducted through the pressure plate to the earth. The seismic signal is detected then amplified, filtered, converted and then processed. The use of a continuous signal enables the processing unit to identify the frequency of the signal with a very low error rate, using frequency content identification. The disclosure also describes a method for transmitting seismic waves through the earth using the above described system.

Abstract: A method of estimating the impulse response of a channel is disclosed. The method includes transmitting an impulse signal to the channel, detecting a received signal from the channel at a receiver, and calculating an estimate of the impulse response of the channel by applying a calculated inverse matrix of the impulse signal to the received signal.

Abstract: A switching circuit for an electromagnetic source for generating acoustic waves has at least one first capacitor connected in parallel with a series circuit formed by a second capacitor and an electronic switch. The switching circuit is connected to a coil of the electromagnetic source, and the first and second capacitors are switched so as to both discharged into the coil, thereby supplying the coil with current.

Abstract: A system and method for controlling operation of a transducer circuit, e.g., including an acoustic transducer arranged to cause mixing, cavitation or other movement in a liquid contained in a vessel located remote from the transducer. A load current of a transformer used to generate a drive signal for the transducer may be controlled to vary sinusoidally, to vary between negative and positive values and such that the load current flows in a closed loop when a zero voltage bias is applied across the primary transformer winding, to have a reduced or eliminated 3rd harmonic mode and/or to vary between three discrete modes including a forward current mode, a zero voltage loop current mode, and a freewheel current mode. An inverter circuit may be used to control the load current, e.g., so that the load current flows in a closed loop during portions of the control cycle.

Abstract: Electronic circuitry for high-power, high-frequency excitation of electromagnetic acoustic transducers (EMAT) without the use of a matching transformer is described. This circuit contains a least 4 switching devices such as power Mosfet transistors, arranged in an H-Bridge configuration that are designed to drive various EMATs over a wide range of frequencies. The switching devices can be connected in parallel with respect to the H-Bridge and switched in sequence for greater power output and variety of wave forms. This circuit configuration can provide a many excitation waveforms including, Churp, Hemming window tone burst, rectangular tone burst and Barker Code wave forms. An improved electronic pulser circuit based on the H-bridge topology is designed for driving the sensor coils of an electromagnetic acoustic transducer (EMAT) to correct the disadvantages of conventional H-bridge pulsers and pulsers that require the use of an output transformer.

Abstract: An object is to provide a modulation device, a demodulation device, and a transmission system and acoustic signal transmission method using them which can carry out a synchronization process for data signals without using a carrier frequency for a synchronization signal. A modulation device 3 transmits an acoustic signal superposed with a PN sequence set according to a carrier frequency and a data signal. A demodulation device 9 receives the acoustic signal, determines the PN sequence having the highest maximum correlation value with the acoustic signal in a plurality of PN sequences, detects a symbol synchronization point according to the correlation value between thus determined PN sequence and the acoustic signal, and performs a synchronization process. Thereafter, according to the detected synchronization point and determined PN sequence, an OFDM demodulation processing unit 38 decides the carrier frequency band of the data signal superposed on the acoustic signal and demodulates the data signal.

Abstract: This invention provides methods and apparatus for focusing a hypersonic beam to control both a direction and depth of audible information delivery. Signals that are delivered to each of a plurality of hypersonic transducer elements are adjusted in phase so that transmitted hypersonic signals are focused at a focal point anywhere in space. The focal point of a focused hypersonic beam may be used to scan a space of interest when used in a receive mode in a pinging process. When objects are detected, a focused hypersonic beam may be used to deliver audible information substantially only to a neighborhood of the detected object.

Abstract: An apparatus and method for wireless communication using an acoustic signal in a system including a first device including a loudspeaker and a second device including a microphone. The first device generates wireless communication information, converts the wireless communication information to an acoustic signal, and transmits the acoustic signal to the second device using the loudspeaker. The second device receives the acoustic signal using the microphone, extracts the wireless communication information from the acoustic signal, generates an acknowledgment signal according to the extracted wireless communication information, and transmits the acknowledgment signal to the first device on a wireless communication channel.

Abstract: An apparatus and method are provided for transferring data through a submarine hull or other solid boundary using high frequency acoustic signals, so avoiding penetration of the hull or boundary. First and second transducers are mounted on opposed surfaces of the hull and aligned to communicate acoustic signals through the hull. The first transducer is driven by a continuous wave carrier signal modulated with data. A demodulator detects that data in the modulated acoustic signals received by the second transducer. Critically, the dimensions of the first and second transducers and the frequency of the carrier signal are selected so as to reduce the interference by triple transit signals through the hull to a level sufficiently low to enable continuous communication of data through the hull at a bit rate of at least 1 MHz. Carrier signals of the order of 40 MHz may be used to achieve data bit rates of the order of 15-18 MHz through the hull.

Abstract: Apparatus for communicating information across a solid wall has one or two outside ultrasonic transducers coupled to an outside surface of the wall and connected to a carrier generator for sending an ultrasonic carrier signal into the wall and for receiving an output information signal from the wall. One or two inside ultrasonic transducers are coupled to an inside surface of the wall and one of them introduces the output information signal into the wall. When there are two inside transducers inside the wall, one receives the carrier signal and the second transmits the carrier after it is modulated by the output information from the sensor. When there is one inside transducer, the output information from the sensor is transmitted by changing the reflected or returned signal from the inside transducer. A power harvesting circuit inside the wall harvests power from the carrier signal and uses it to power the sensor.

Abstract: A diver unit computes the direction and distance to a specified target. When the target is obstructed, the diver unit receives navigation assistance data from another diver unit. The navigation assistance data includes direction information that is referenced to a common reference line extending between the two diver units.

Abstract: A system and method for communications in a mine provides for seismic wave generation through mine strata which may include specific location identification within the mine can be used in emergency situations by trapped miners. A seismic transmitting transducer may impart seismic waves onto a rod embedded into the strata, which is tunable by use of a slideable manifold that couple the transducer to a rod. Likewise, a receiving transducer which may also be coupled to a rod via a manifold may be configured to receive the seismic wave. The seismic wave may be modulated to produce a message or portion of a message that may be decoded at the receiving location. The transducers may be configured to utilize frequency hopping spread spectrum techniques. A geophone may be used as the receiving transducer.

Abstract: An intelligent packaging system utilizing acoustic wave devices includes an electronic module, a SAW ID, various passive SAW sensors and a printed antenna. The passive SAW sensors include a SAW pressure sensor, a SAW temperature sensor and one or more SAW chemical sensors for monitoring physical parameters of a package content. The electronic module generally includes a printed large area distributed electrical circuit, an impedance transformer and a SAW transponder for realizing passive wireless monitoring of the structural integrity of the package. A separate power harvesting antenna and/or a separate dual band antenna can generate radio frequency (RF) power for biasing components associated with the electronic module.

Abstract: Disclosed are a position tracing signal generator unit and an input system using the same. The position tracing signal generator unit of the present invention generates ultrasonic signals with a constant time interval to allow ultrasonic signals generated from a plurality of ultrasonic signal generator to be overlapped and amplified. It is possible to increase the intensity of the ultrasonic signal and lengthen the range. Due to the structural advantages of the present invention as described above, it is possible to solve a problem of the prior art, i.e., a large thickness of the position tracing signal generator unit caused by a large size of the ultrasonic sensor for increasing the intensity of the ultrasonic signal.

Abstract: The disclosed system uses seismic signaling to locate survivors in a mine collapse. A separate transmitter with a specific pre-selected frequency or frequencies is placed in pre-positioned safety zones of a mine. The system generates frequency-locked, unmodulated seismic energy, which allows rescuers to identify the safety zone where a transmitter is activated. The transmitter comprises an oscillator that generates the signal. The oscillator drives the transducer. The transducer causes the inertial mass to move. The movement of the inertial mass generates the seismic waves, which are conducted through the pressure plate to the earth. The seismic signal is detected then amplified, filtered, converted and then processed. The use of a continuous signal enables the processing unit to identify the frequency of the signal with a very low error rate, using frequency content identification. The disclosure also describes a method for transmitting seismic waves through the earth using the above described system.

Abstract: A suppressed feature waveform sonar transmission is produced by modulating a carrier wave with a baseband waveform that is generated from a known pulse sequence. A waveform embodiment of the pulse sequence is modified to create interference among the primary lobes of the constituent waveforms that are representative of the individual pulses. The baseband waveform so created appears as noise, making the baseband waveform modulation of the sonar transmission difficult to detect without knowledge of the pulse sequence or baseband waveform structure. The sonar transmission can be analyzed by cross-correlating the received signal with the baseband waveform or the pulse sequence waveform. The pulse sequence is preferably a complementary sequence. Modification of the pulse sequence may be obtained by passing an embodiment of the pulse sequence through a bandpass filter.

Abstract: A method and system of producing a parametric ultrasonic wave to be decoupled in air to create a decoupled audio wave that closely corresponds to an audio input signal. The method is comprised of ascertaining 402 a linear response over a predefined frequency range of an acoustic output of an electro-acoustical emitter to be used for parametric ultrasonic output. A parametric ultrasonic processed signal is then created by adjusting 404 linear parameters of at least one sideband frequency range of a parametric ultrasonic signal to compensate for the linear response of the acoustic output of the electro-acoustical emitter such that when the parametric ultrasonic processed signal is emitted from the electro-acoustical emitter, the parametric ultrasonic wave is propagated, having sidebands that are closely matched at least at a predefined point in space over the at least one sideband frequency range.

Abstract: A PWM signal generator is operable to generate a first pulse signal and a second pulse signal at least one of before and after generating the first pulse signal. A duty ratio of the second pulse signal is gradually changed. A low-pass filter is operable to convert the first pulse signal output from the PWM signal generator into an analog acoustic signal. The low-pass filter is operable to convert the second pulse signal output from the PWM signal generator into the analog acoustic signal having an inaudible frequency.

Abstract: To provide a surface elastic wave apparatus that suppresses occurrence of fine ripples within a pass band, improves insertion loss and enhances the degree of balance. First and second surface acoustic wave elements (14, 15) that are parallel-connected to a surface acoustic wave resonator (16) respectively have three or more odd-numbered IDTs (2-4, 5-7), each having a plurality of electrode fingers placed along a propagation direction of a surface acoustic wave that is propagated over a piezoelectric substrate (1), and reflectors (8, 20, 21, 10), each having a plurality of electrode fingers that are placed on the two ends of the IDT row, and among all the electrode fingers respectively possessed by the IDTs and reflectors, the polarities of the electrode fingers placed adjacent to a different IDT or reflector are arranged symmetrically centered on the IDT located in the center.

Abstract: The force exerted by a reciprocating actuator is estimated as a weighted sum of three quantities: a reaction-mass acceleration, a baseplate acceleration, and a relative acceleration of the reaction-mass relative to the baseplate. In one embodiment, acceleration sensors measure the reaction-mass acceleration and the baseplate acceleration; and a displacement transducer measures a relative displacement of the reaction-mass relative to the baseplate. A double-differentiator generates the value of the relative acceleration from the second derivative of the relative displacement. In the sum, the relative acceleration is weighted by factor representative of the ratio of the difference between the masses of the reaction-mass and the baseplate to the sum of the masses of the reaction-mass and the baseplate.

Abstract: In a method and apparatus for defense against missiles that have explosive substances and piezoelectric detonators, the detonator of the missile is excited by ultrasonic radiation, causing it to oscillate and thus be triggered in flight.

Abstract: An acoustic signal transmission system of the present invention is a system for transmitting information via sound waves, and has a modulation device, a plurality of speakers, a microphone and a demodulation device. The modulation device generates transmission acoustic signals by encoding transmission signals based on a transmission diversity method and allocating the encoded transmission signals to a plurality of transmission paths. The plurality of speakers output the transmission acoustic signals as sound waves respectively based on the allocation. The microphone receives the sound waves which are output from the plurality of speakers, and outputs received acoustic signals. The demodulation device decodes the received acoustic signals based on the transmission diversity method by using a transfer function of the each sound wave from the plurality of speakers to the microphone.

Abstract: A system and method for measurement are disclosed which may include providing an input command signal; convolving the input command signal with a plurality of impulse signals to produce a transducer drive signal; and activating a first pressure transducer with the drive signal to transmit a pressure wave output from the transducer.

Abstract: A technique is provided by which energy is physically/mechanically transmitted down through a wellbore. The transmitted energy is directed downhole along a fluid channel and impinges on an energy converter positioned in the wellbore or at another subterranean location. The energy converter converts the physical energy into electrical energy that can be supplied to a downhole device.

Abstract: Low probability of marine mammal impact (LPMMI) sound signals have a modulation component selected to reduce a behavioral response from a marine mammal from that which would occur when transmitting another sound signal having approximately the same time duration component, approximately the same bandwidth component, and approximately the same center frequency component as the LPMMI waveform but having a modulation component comprising a frequency modulation.

Abstract: An ultrasonic transmitter system(s) and method(s) are described having location and tracking capabilities. The transmitter's, by using ultra sound and encoded micro-modulation, are able to provide enhanced longevity and reliability. A maze algorithm is devised that further provides discrimination of false detections, versus true detections, and no detection.

Abstract: This invention relates to signal processing and to acoustics. The invention provides a method of amplitude modulating a message signal (12) in the audible frequency range of a human onto a carrier signal (14) in the ultrasonic frequency range, the method including generating an amplitude modulated signal (20.1) having a constant envelope on one side (72). The invention extends also to a method of amplitude modulating a message signal (12) in the audible frequency range of a human onto a carrier signal (14) in the ultrasonic frequency range, the method including generating an amplitude modulated signal (20.2) having a constant level (33) defined successively by an upper and lower envelope of the amplitude modulated signal (20.2). The invention also extends to related amplitude modulators (10) and (110) and also to a related acoustic system (50).

Abstract: Provided is a system for characterizing complex acoustic waves having: means to read an existing configuration file containing saved parameters or create a new configuration file with no previous parameters; means for defining an actuation carrier, selecting the wave shape, and specifying the associated parameters; means for defining the propagation control signal; means for defining the propagation control signal repeat rate; means to produce a resultant actuation signal and, optionally, output resultant actuation signal as a file; and, for multiple carriers, means to define the multiple carrier stagger and referenced actuation signal. Optionally, further provided are means to input a frequency response as a function of frequency and distance; means to define a distance; and means to produce an effective actuation signal derived from the resultant actuation signal, the frequency response, and distance.

Abstract: A system and method simultaneously transmits sound waves through a plurality of sonar elements without interference, such as for the purpose of tracking objects underwater. The system has a pulse generator with a plurality of transceivers connected to the pulse generator. A plurality of sonar elements is connected to the plurality of transceivers, with at least one sonar element per transceiver. A sonar signal is sent from the pulse generator to each sonar element, passing intermediately through a transceiver.

Abstract: An electrostatic ultrasonic transducer includes a diaphragm having a conducting layer and a pair of first and second fixed electrodes opposed to the corresponding surfaces of the diaphragm, the pair of fixed electrodes having a plurality of through holes in corresponding positions, wherein a DC bias voltage is applied to the conducting layer of the diaphragm and an alternating current signal is applied between the first and second fixed electrodes to generate an ultrasonic wave. Part of the pair of fixed electrodes includes s driving fixed electrode for driving the ultrasonic transducer, and the other part includes a detecting fixed electrode for detecting the amplitude of the diaphragm. The ultrasonic transducer includes a control unit that controls the vibration of the diaphragm so that the amplitude is proportional to the input signal based on the amplitude of the diaphragm detected by the detecting fixed electrode.

Abstract: In a method and apparatus for defense against missiles that have explosive substances and piezoelectric detonators, with the detonator of the missile is excited by ultrasonic radiation, causing it to oscillate and thus be triggered in flight.

Abstract: A driver circuit for generating a driving pulse signal to activate a vibrating element includes a half-bridge circuit formed essentially of first and second switching devices to which drive signals are supplied through a driver interface. A driving voltage is supplied to a source of the first switching device, a drain of the second switching device is grounded, and an output terminal of the half-bridge circuit is connected to the vibrating element. The half-bridge circuit is controlled such that the two switching devices alternately turn ON. When the first switching device is ON, the driving voltage is supplied as the driving pulse signal to the vibrating element, and when the second switching device is ON, the vibrating element and the second switching device together form a low-impedance closed loop. As the switching devices are caused to alternately turn ON at specific intervals, the vibrating element vibrates at a natural resonant frequency, transmitting thereby an ultrasonic signal.

Abstract: An apparatus and method for seismic data acquisition is provided, which, in one aspect, define a plurality of attributes relating to acquisition of seismic data by the apparatus, determine a value of each attribute when the apparatus is deployed for acquiring seismic data, generate a message for each attribute whose determined value meets a selected criterion, and transmit wirelessly each generated message to a remote unit without solicitation of such a message by the remote unit. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

Abstract: A hydrophone array includes hydrophones having an electret means and may have TFT FETs to generate current in response to received longitudinal wave signals. The arrangement may also be used to transmit longitudinal wave signals. Storage capacitors may be coupled to each TFT FET output to act as sample and hold means. Digital switches may allow the sample and hold circuit to both reset and measure the output of the hydrophone element. Data lines may be used to indicate the location of the received signal on the longitudinal wave detector sensor array.

Abstract: A system and method for measurement are disclosed which may include providing an input command signal; convolving the input command signal with a plurality of impulse signals to produce a transducer drive signal; and activating a first pressure transducer with the drive signal to transmit a pressure wave output from the transducer.

Abstract: A driver circuit for generating a driving signal by pulse-width modulation (PWM) includes a half-bridge circuit formed essentially of a pair of series-connected FETs. When the level of an ultrasonic signal, or of the driving signal, is to be maximized, the individual FETs are switched at a switching frequency matched to the frequency of the driving signal. When the level of the ultrasonic signal, or the driving signal is to be reduced, on the other hand, the individual FETs are switched with specific timing determined based on the frequency of a clock signal of which period is shorter than that of the driving signal.

Abstract: Birds carry many parasites and other diseases, which pose a health risk to humans which come into contact with their habitat. However, ultrasonic waves agitate and deter birds and other pests from roosting in nearby areas. The disclosed device utilizes solar energy to power a battery pack, which in turn activates both a tone generator and its adjoining amplifier to create and emit the annoying ultrasound. In this way, birds are dissuaded from gathering in particular areas where the ultrasonic device is in use, and humans are provided a more healthy and disease-free environment.

Abstract: A system configured to dynamically adjust the ultrasonic carrier level in a parametric array system in response to changing source signal input levels, and which employs a look-ahead delay strategy to enable optimal modulation of the carrier wave to eliminate constant ultrasonic carrier emission and reduce the ultrasonic carrier emission to what is actually needed to accommodate the db range of the source material, and at the same time, to also minimize noticeable distortion and sound artifacts of a high-power ultrasonic carrier, and/or distortion/artifacts arising from modulation of an ultrasonic carrier to reduce average power output; and thus it realizes advantages of carrier modulation based on source-signal level, while minimizing inherent drawbacks of carrier modulation.