Abstract: An acoustic mouse system is described that controls indications on an X-Y surface of the face of a display. The system comprises a support for holding at least three acoustic receivers in an x-y plane, and a hand movable acoustic transmitter that is movable both parallel to the x-y plane and in a z direction perpendicular to the x-y plane. The transmitter generates periodic acoustic oscillations in the direction of the support and its receivers. Detection circuitry, responsive to signals from the acoustic receivers, provides signals indicative of the absolute position of the acoustic transmitter in the x-y plane. A processor is responsive to the signals from the detection circuitry to provide absolute position signals to the display, whereby the display responds by moving an indication to a corresponding position on the X-Y surface of the display face.

Abstract: A method is disclosed for determining the separation between a seismic energy source and a seismic sensor, the location of which is known imperfectly. After the source emits a wavefield, the first-arriving impulse at the sensor is statistically processed to form a range statistic that is related to the true travel time between the source and the sensor. A set of range statistics from a plurality of source positions are filtered and converted to range loci, the intersection of which marks the location of the sensor.

Abstract: A method and apparatus for compensating sensitivity fluctuations in signals received from respective groups of hydrophones for the purpose of subsequent signal processing, the groups being arranged in a predetermined sequence (0, 1, 2, . . . i) to form a transducer arrangement, wherein the received signals are influenced by the sensitivity of the hydrophones and/or the gain of preamplifiers connected to the outputs of the hydrophones. The energy value (W.sub.i) for the received signals of each group of hydrophones is determined and a median energy curve (W.sub.m (.theta.)) is derived from the energy values (W.sub.i) as a function of the sequence of the groups of hydrophones. A correction value is formed for the signals received from each group of hydrophones from a comparison of the respective energy value (W.sub.i) with the energy curve (W.sub.m (.theta.)) and the received signals are corrected with the correction value.

Abstract: The source region of a volcanic tremor is determined by simultaneously detecting the tremor using seismometers installed at at least four separate points, obtaining correlation functions among pairs of the detected values, calculating at least three observation time lags corresponding to the maximal values of the correlation functions, and using the at least three observation time lags for determining the source region of the volcanic tremor.

Abstract: An apparatus and method for determining the position of a movable element. An elongated housing is provided for positioning generally adjacent an edge of an area in which the position of the movable element is to be determined. The housing has a base portion which contains a pair of spaced-apart transducers that are mounted in the surface of the base portion and face the area. An upper body portion of the housing is disposed above the base portion and protrudes in cantilevered fashion toward the area, so that the transducers are recessed from the area beneath the protruding upper body portion of the housing. Circuitry is provided for determining the position of the movable element from the respective transit times of energy propagating in either direction between the movable element and the pair of transducers.

Abstract: Apparatus located aboard a platform situated in an acoustic environment for racking a moving body when the body is proximate to the platform. The apparatus includes a selected number of acoustic sensor elements at selected locations around the platform, each of the elements for detecting acoustic information arriving at its selected location. The apparatus further includes signal conditioners coupled to the sensor elements, a given one of the signal conditioners providing a conditioned signal representing acoustic information which is emitted by the moving body when the body is proximate to the platform, and which arrives at the location of the acoustic sensor element to which the given signal conditioner is coupled.

Abstract: This invention is an automatic gunnery system, responsive to airborne acoustic shock waves produced by a projectile passing through a target area. Curved elongated acoustic energy conductors are located adjacent to one side of said target area with acoustic transducers attached to the end portions thereof. Said transducers produce an electrical signal when a shock wave from the projectile reaches them through said energy conductors. Electrical signal from the transducers is connected to electronic circuitry which determines the location of each "hit" on or near the target which is registered on display means.

Abstract: Hydrophones are installed in each tank of a liquid cargo tanker ship. In the unfortunate event that the tanker collides with an obstacle in the water, the hydrophones detect the shock wave due to the collision. The relative first arrival times of the shock wave at the respective hydrophones are measured and the arrival-time differences between two hydrophones of any two different selected pairs of hydrophones is calculated. Hyperbolic lines of constant time difference are projected on a map of the locations of the hydrophones on the ship. The intersection of the lines of position representing the calculated first arrival time differences marks the location of the impact of the ship with the obstacle.

Abstract: Apparatus and method for sonar or radar target tracking. Digital apparatus nd techniques are employed. A variable delay is used for beam steering.

Abstract: A compensating beamformer which requires orders of magnitude fewer calculations that prior art methods. A compensating beamformer is provided which comprises a plurality of sensing elements and a plurality of analog-to-digital converters, for converting incoming analog signals to digital form. Digital signals from at least four such elements are used to compute phase angle information which is combined to form a matrix of input data in the frequency domain. An unweighted steering vector is determined to sample data from the target direction. A corrector matrix is calculated based on input data from sensing elements. That corrector matrix along with its inverse, which is determined recursively, is used in combination with the unweighted steering vector to determine an optimal steering vector. The input data in the frequency domain are then multiplied by the optimal steering vector to obtain signals in the directions of interest.

Abstract: The invention described herein relates generally to the field of signal processing for signal reception and parameter estimation. The invention has many applications such as frequency estimation and filtering, and array data processing, etc. For convenience, only applications of this invention to sensor array processing are described herein. The array processing problem addressed is that of signal parameter and waveform estimation utilizing data collected by an array of sensors. Unique to this invention is that the sensor array geometry and individual sensor characteristics need not be known. Also, the invention provides substantial advantages in computations and storage over prior methods. However, the sensors must occur in pairs such that the paired elements are identical except for a displacement which is the same for all pairs. These element pairs define two subarrays which are identical except for a fixed known displacement.

Abstract: A planar end-fire acoustic transducer array is composed of a planar matrix f individual elements. In order to give this array an end-fire characteristic, predetermined elements are provided with outputs which are phase-inverted with respect to the outputs of the other elements of the array, the sum of the gains of these predetermined elements being made equal to the sum of the gains of the other elements.

Abstract: An apparatus is disclosed for determining the position of a moveable element in a three-dimensional workspace near a mounting surface. A sound source is provided in the moveable element. A plurality of at least three housing units are adapted to be secured to said mounting surface in spaced relationship to one another. A sound sensor is mounted on each of the units, and a sound source is mounted on at least some of the units. The positions of the sound sensor and the sound source of said at least some of the units can be adjusted. Means are provided which are responsive to the sound from the sound source of at least one of the units and received at the sound sensor of another of the units, for computing the distance between the sound source of said one of the units and the sound sensor of said another of said units.

Abstract: A system of three or more hydrophone arrays are utilized to measure underwater areal sound intensity. The hydrophone arrays bound at least one plane through which an areal sound intensity measurement is desired. Each hydrophone array comprises three orthogonal pairs of hydrophones with coincident acoustic centers. The output of each hydrophone in the system is simultaneously sampled and the outputs processed to obtain a vectorial sound intensity representation at each of the hydrophone arrays from which a representation of the areal sound intensity across the noted plane may be derived.

Abstract: The depth of a cavity or chamber (10') is measured by using the chamber as the resonator of an electronic oscillator (24) whose oscillations are coupled to fluid in the cavity by transducers (12, 13). Both the variable-depth main chamber (10') and a reference chamber (117) of fixed depth are measured. Variations in the data obtained from the chambers are caused by factors affecting the velocity of propagation of sound in the fluid. An accurate measurement of the depth of the main chamber is obtained by compensating direct data (at 42) obtained from the main chamber (10'), using, data (at 43) obtained from the fixed-depth reference chamber (117). In one embodiment an inertance orifice (121) is utilized between the two chambers. The fluid inertance of the orifice, together with the compliance of the fluid in the main chamber (10'), form a resonant system whose anti-resonant frequency is a measure of the dimensions of the main chamber. (Inertance is the acoustical equivalent of inductance.

Abstract: A hydrophone (16) having a short-baseline array of transducers (12A, 12B, and 12C) as well as a long-baseline array of transducers (14A, 14B, and 14C) includes switches 30A, 30B, and 30C) for selectively connecting the outputs of the arrays to a cable (18) that carries the signals to processing circuitry (20) aboard an ocean-going vessel (24). The switches (30A, 30B and 30C) change state in accordance with the output of a narrow-band filter (42), which indicates whether the received signal is of a predetermined frequency and thus is likely to have been produced by an intended source. Due to the delay inherent in the narrow-band filter 42, the processing circuitry (20) thus processes the response of the long-baseline array to the first part of a beacon pulse and the response of the short-baseline array to the second part of the beacon pulse.

Abstract: In order to locate a source of acoustic emissions, two multi-element transducers are employed. The elements of each transducer are subjected to an impinging acoustic wave at different moment in time depending upon the angle of the wave. Outputs from the elements of each transducer are compared with a look-up table to determine the angle. Then, another look-up table is used to determine the X-Y intersection of impinging wave angles from both transducers which locates the source.

Abstract: A coordinate inputting device in which the vibrations imparted from a vibration pen to a vibration transmitting plate are detected by a plurality of vibration sensors so as to enable the coordinates of a vibration input point to be detected using the time it takes for the vibrations to propagate on the vibration transmitting plate. The vibration transmitting plate has noise interrupting means for preventing noise coexistent with the vibrations imparted by the vibration pair for coordinate detection from being input to the vibration sensor.

Abstract: Apparatus 10 (FIG. 1(a)) for providing acoustic power spectra, all defined over a frequency band from signals received in a predetermined time interval, for individually identifiable directions comprises a pair of arrays 11, 11' of omnidirectional microphone elements 12. The time interval is divided into sampling periods and for each period the microphone signal sampled at 17, digitized at 21 and applied to array sample storage means 27 comprising corresponding shift register 28.sub.1. . . 28.sub.N for each microphone channel. Previously applied samples are clocked one stage with each new sample so each stage represents a delay of one sampling period. Register stages are connected to nodes 34 of a switching matrix 33, selected by ROM 36 to define the relative delays between samples for each beam direction and those samples read by the matrix are combined to form directed beam samples for that sampling period, stored at 40.

Abstract: For marking and finding weld seams to be investigated under water ultrasonic transmitters 54 are provided which have luminous or light-reflecting characters 58. The diver brings an ultrasonic receiver 60 up to the ultrasonic transmitter 54. For more exact location determination along the weld seam 52 a tape is provided which is disposed along the weld seam 52 and has elements arranged in coded manner.

Abstract: A vibration which is input to a vibration propagating plate by a vibration pen is detected by vibration sensors attached at corner positions of the plate. This vibration is propagated as elastic waves in the vibration propagating plate and reaches the sensors. The coordinates of the vibration input point are calculated on the basis of the vibration propagating times corresponding to the detection signals from the sensors. The vibration sensors are come into pressure contact with the vibration propagating plate through a fluid like a grease having a high viscosity or consistency. Since such a fluid is filled in the space which is formed between the pressure contacting surfaces of the vibrator and vibration propagating plate, their coupling states are stable and the vibration and coordinates detecting characteristics can be uniformed every product.

Abstract: The position of a projectile travelling at a supersonic velocity is sensed by two triangular arrays of transducers 10,11 which are located below and close to the plane of a target area 14 through which the projectile passes. Signals from the transducers are processed to obtain data indicative of the direction of the trajectory from each array. This data can be processed to obtain the position of the trajectory in a cartesian coordinate system.

Abstract: An aircraft detection system which detects and tracks aircraft using: arrays of seismic and acoustic sensors, a set of junction circuits, a set of subarray circuits, several slave computers, and a master computer. Each junction circuit relays detected signals from several adjacent sensors to a subarray circuit and command signals to each of the sensors to adjust the gain of their output signals. Each subarray circuit receives and unites the outputs of several adjacent junction circuits into a subarray which has a particular geographical location in the array of sensors. Each slave computer forwards detected signals from single subarray circuit to the master computer, and relays command signals back to each individual sensor. Each subarray is able to track the seismic or acoustic signature of an aircraft as it travels across the regular distribution of sensors. Each subarray is thereby able to define an azimuth to the target aircraft.

Abstract: A visual environment simulator for a viewer moving about in a device implementation space. A display screen shows the viewer images of another environment. An array of three separately positioned ultrasonic transmitters sends intermittent signals to each of three ultrasonic receivers in order to monitor the change in the spatial coordinates and the orientation angles of the viewer and/or mobile unit(s) carrying or carried by the viewer. Digital circuitry is provided for sending and receiving sonic signals in a predetermined time sequence, and for sending a cue pulse to accurately initiate the counting of the transit time for each separate sonic signal. The transit time data are processed and revised video images are shown to correspond with the change of location (3-dimensional translational displacements) and change of orientation (3-axis rotational displacements) along and about the line-of-sight of the viewer.

Abstract: A method of determining the bearing "S" of a signal transmitter relative to a remote signal receiver. A signal pulse having a high signal to noise ratio is transmitted and sampled at closely spaced receivers displaced from the transmitter by a distance "D". Sampled phase components are derived at each receiver by deriving in-phase and quadrature components of the sampled pulse and by deriving the arctangent of each such component. The arrival time of the sampled pulses is measured by applying a least squares Gaussian fit to the modulus or to the amplitude envelope of the pulse samples. The difference ".delta.t" between the time of arrival of the pulse at each receiver is determined and then the approximate phase difference 2.pi..omega..delta.t between the sampled pulses is determined where ".omega." is the carrier frequency of the transmitted pulse. The phase difference is then applied to resolve the phase ambiguity of the phase components and the bearing "S" is then calculated.

Abstract: A seismic exploration method and system employing a streamer that houses at least one pair of orthogonally mounted hydrophones. The streamer may be operated downhole in a well, or may be towed in a body of water by a marine vessel. In the downhole embodiment, the invention permits detection of seismic signals of interest with suppression of noise due to tube waves and (dipole and monopole) modal waves propagating in and along the well, and without the need for locking the seismic detectors to the wall of the well. In the marine embodiment, the invention permits selective detection of waves incident from any incidence direction of interest (including the horizontal and vertical directions). In all embodiments, the incidence angle of the detected seismic wave is determined. The amplitude of the detected wave may also be determined from the incidence angle and the amplitude components detected at each hydrophone.

Abstract: A method for locating signal sources, particularly sound signal sources, is suggested using several spacially separated sensors whose output signals are processed in order to detect noise and to eliminate such noise under utilization of a normalizing factor, the normalizing factor considers particularly those frequencies which, for one reason or another, are uniquely attributable to noise.

Abstract: A system for deploying an array of sonar projector transducers includes a housing in which a plurality of disk shaped projectors are stacked, a pair of small diameter cables are reeled from a powered drum for tethering the projectors, the cables being anchored to the bottom projector, a pair of electrical conductors are connected to the projectors, each conductor constituting a series of sections interconnecting electrical connectors fastened to opposite sides of each projector, a centering ring attached to the bottom projector including a series of pressure responsive latches which serve to secure the array in the housing and to release the array upon its reaching a desired depth. Where the drum is actuated the stack is lowered with each projector being successively suspended by its pair of conductor sections, and each of the conductor sections is given a predetermined twist such that when the array is again returned to the housing the conductor sections are caused to form predetermined loops.

Abstract: There is disclosed an inspection system which allows the visual inspection of an item and the automatic recordation of the position of a defect or other inspection characteristic in the plane of inspection. In the visual inspection of an electronic circuit card, the card is inserted into a holder which maintains the card in a reference plane which is fixed relative to a plurality of sonic emitters. A microscope or other viewing device is fixed in a predetermined position on a support structure and includes cross hairs or other indicia to allow the visual identification of a particular point on an item that is to be visually inspected. A plurality of sonic receivers are coupled in predetermined positions on the support structure to receive sonic energy generated by the emitters.

Abstract: Hydrophone systems in which the direction of acoustic waves impinging on an array of hydrophones is determined from measurements of the periods between successive zero-crossings of waves detected by the two hydrophones of each several different pairs of the hydrophones, allowance being made for the fact that the start and finish of such a period may be due to zero-crossings of different waves. In one embodiment the hydrophones are arranged in two linear groups disposed at right angles to one another, with unequal spacing between adjacent pairs of hydrophones in each group. In another embodiment the hydrophone array consists of five hydrophones disposed at the corners of a regular pentagon.

Abstract: A small non-colinear transducer array for omnidirectional acoustic emission monitoring is disclosed. The small transducer array consists of four piezoelectric sensor elements of sufficiently small diameter as to function as essentially point receivers and of sufficient frequency response as to be sensitive to the signals to be detected. The sensor elements of the transducer array are close together and are non-colinear so that the signals received by them can be used for determining the group velocity of acoustic waves on solid plates and on plate-like structures such as shells and pipes, and to permit determination of both the source direction and distance.

Abstract: Method and apparatus for evaluating location of an unknown sound generated in a structure such as a pressure vessel. A plurality of sound detectors are mounted on the structure for detecting sounds generated in the structure. On the basis of sound information of the unknown sound source derived from the outputs of the detectors, the location where the unknown sound is produced is determined. To this end, reference sounds are first generated at a plurality of known reference sound source positions, wherein information of the reference sounds derived from the outputs of the detectors are stored in a storage unit. Equi-pattern-distance curves each of which is in an equal pattern distance between a supposed unknown sound source and each of the reference sound sources are calculated on the basis of the reference sound information. The equi-pattern-distance curves are further corrected in accordance with the reference sound information.

Abstract: An apparatus and method for detecting the direction of a sound. A thin shell structure is permitted to flex in response to incident sound and perturb the form of the shell. The perturbation is detected and from this the direction of the sound can be determined.

Abstract: A method of determining both the level of sound occurring at a point in an area of interest and the location of the point. The level of sound at a point in the area of interest is sensed, and a first signal is transmitted from the point. This first signal is received at a first location related to the area of interest, and the direction relative to the first location from which the first signal was transmitted is determined. A second signal is transmitted from the first location which is indicative of the direction relative to the first location from which the first signal was transmitted. Similarly, the first signal is received at a second location related to the area of interest. The direction relative to the second location from which the first signal was transmitted is determined, and a third signal is transmitted from the second location which is indicative of the direction relative to the second location from which the first signal was transmitted.

Abstract: A phased-array sound pickup apparatus has an array of directional microphones having individual directivity patterns equally oriented in a given direction. The directivity patterns of the microphones combine into the main lobe of the array. A plurality of variable delay circuits are connected to be responsive respectively to individual signals from the microphones for providing incremental delays to the individual signals and combining the delayed signals for delivery as an output of the apparatus. A delay control circuit is coupled to the variable delay circuits for generating a delay control signal for controlling the amount of the incremental delays to cause the main lobe to be steered at an angle to the given direction as a function of the delay control signal.

Abstract: A beamformer device for forming at least one beam from the outputs of a sensor array, including: a plurality of radiation sources; means for providing to each radiation source a signal from an associated one of the sensors in the sensor array; a detector array of radiation-sensitive means for providing a series of spaced signals representing radiation incident from each of the radiation sources; and means for varying the delays between the spaced signals for optimizing the response of the device to a signal from a predetermined direction.

Abstract: A system for detecting and identifying acoustic sound sources using a pluity of identical data acquisition modules spaced at preselected intervals along a line array. Two small diameter coaxial cables provide intermodular connections for power, timing control and sequential data transmission to a remote receiver. A control clock waveform leading edge simultaneously triggers sampling and holding of sensor data at each module of the array while the waveform trailing edge is delayed for a preselected interval at each module to provide squential data output.

Abstract: A direction indicator giving a visual indication of the direction of origin of incident sounds having frequencies in a predetermined frequency range, is disclosed herein. The direction indicator embodies at least three sound detectors, each having an active filter passing electrical signals in a predetermined frequency range and a light emitting diode giving a visual indication of the intensity of the sound in the predetermined range received by the associated sound detector. Two of the sound detectors are disposed to preferentially receive sounds from opposite directions, and the third sound detector is disposed to receive sounds originating from a third direction normal to the directions of the first two. In the preferred embodiment, the direction indicator is an emergency vehicle direction indicator for use in an automobile giving the operator a visual indication of the direction of an emergency vehicle sounding its siren.

Abstract: An acoustic line array which includes a co-axial cable having a center coctor surrounded by a flexible material of low-electrical conductivity. The flexible material is surrounded by a conducting material protected by an external shield. The cable has characteristic impedance which is sensitive to pressure variations in the medium due to a traveling acoustic pressure wave from an acoustic source. Variations in the impedance of the array are used to detect the acoustic source. Alternatively, the line array makes use of discrete sensors placed at suitable intervals along the array. This type of acoustic array eliminates the use of a plurality of wires carrying the electrical signals from the transducer to the storage equipment and elaborate multiplexing techniques.