Hydroacoustics, Inc.

Hyroacoustics, Inc.

John V Bouyoucos

Roger L Selsam

Dennis R Courtright

David E Nelson

David W Durfee

David P Hollinger

Robert F DeLaCroix

Marvin J Behnfeldt

David C Charvoz

Robert O Wilson

A small boat or launch such as a motorized reinforced hull inflatable boat provides a platform for an acoustic source array of airguns. The array is made up as a ladder structure in which the airguns are disposed horizontally between vertical support and umbilical lines, preferably with their discharge ports in laterally offset or staggered relationship to minimize undesirable interactions between the acoustic transmissions released into the water by the sources and to help maximize the acoustic output of the array for a given array length. A structure stows the array on the boat for transport when the array is not deployed for use. If desired, the stowed array may be substantially enclosed by the hull of the boat. The stowage structure is preferable defined by a track or rails on the top of the deck. Umbilical cables attached to the array are translated, as by being wound on a drum and unwound therefrom, to deploy or retrieve the array over the stern of the boat. The umbilicals provide power (compressed air to the airguns and control signals for timed actuation of the guns). The array may be part of a module which includes a winch for winding and unwinding the umbilicals to retrieve and deploy the array. The array system also includes a compressor for supplying compressed air to the airguns of the array.

Acoustic source array system module for underwater operation which can be installed on a motorized boat

In order to optimize detection of targets from a broadband return, a multiplicity of narrow bands are matched-filter processed simultaneously in parallel. The band or bands which provide the best joint combination of target and propagation in response are used for target detection.

Sonar system especially for shallow water application such as in littoral environments

A marine towed array has a plurality of tow bodies of positive buoyancy each containing a marine acoustic source, such as a vibrator source. Each tow body uses a reel containing an electro-mechanical tow cable connecting the sources, whereby reeling and unreeling of the cable, controlled from a towing ship, changes the spacing of the tow bodies. One of the tow bodies at an end of the array is attachable to the towing ship.

Towed acoustic source array system for marine applications

An electrohydraulic pavement breaker system having cavities ( ) which are filled with hydraulic fluid (oil) or gas, and which provide mass spring system which is resonant at a frequency which is especially adapted for breaking and rubblizing concrete pavement. The resonant mass ( ) is in impacting relationship with the pavement through a shoe ( ), which shoe ( ) may be part of an assembly which is pivotally mounted on the support structure ( ) of the breaker and is vibrated with the mass ( ) to repeatedly impact the pavement at the rate of the resonant frequency. An electrohydraulic control system is responsive to the motion and average position of the mass of the vibrator and controls the driving force so as to be at the resonant frequency of the mass spring system and have the amplitude and energy suitable for breaking the pavement.

Vibratory pavement breaker

An acoustic transmission in an underwater environment having a spectrum (amplitude/frequency signature) of interest is generated by cyclically releasing energy which forms impulses which individually have spectral amplitudes principally near one end of the desired spectrum, but which impulses are repeated at a rate near the opposite end of the desired spectrum, which rate may be varied to smooth the spectral response. A multiplicity of impulses may be generated synchronously, the number depending upon the desired amplitude of the spectrum. A multi-port air gun having a stator with a series of ports, which are valved by a rotor coaxial with the stator provides the energy in the form of the release of compressed air bubbles. The rate at which the impulses are produced is controlled by controlling the speed of rotation of the rotor. The amplitude of the transmission may be controlled by means of a ram which moves along the axis of rotation of the rotor to select the number of ports commensurate with the required amplitude of the spectrum. The source may be housed in a tow body and provides a transmission simulating a ship's noise spectrum which may be used as an aid to acoustic mine sweeping.

Underwater acoustic impulse source

A system for geophysical exploration uses a single source (,) which emits signals over multiple octaves. The source is driven by a composite sweep signal having two or more sweeps, one of which covers the lower octave (,) while the other sweeps cover the remainder of the bandwidth. The signals covering the lower portion are reduced in the case of a sweep which varies linearly with time in proportion to the square root of the ratio of the sweep rate of the signals covering the upper end to the sweep rate of the signals covering the lower end. The signals are transmitted simultaneously. Because of the composite sweep the same energy spectrum is transmitted as with a sine wave sweep which extends over the entire frequency band, while reducing the peak power and radiator displacement required at lower frequencies to maintain a flat spectrum. The size of the equipment can be reduced.

Geophysical exploration system using seismic vibrator source which provides a composite sweep

An improved acoustic source array system is provided by the invention to generate acoustic signals underwater. The system has an array of acoustic signal sources, such as air guns, towable while underwater behind a surface vessel. The array includes a plurality of these sources, and spreader bar assemblies including these sources. The sources are attached by these assemblies at predetermined separation distances in the array. The spreader bar assemblies provide manifolds for storing and regulating energy, such as compressed air, to operate the sources. The array is connected to the vessel by an umbilical. The sources are controlled by a shipboard controller for firing the sources to provide acoustic signals underwater at selected times. The array may be towed from the ship with the flat side of the array assuming an angle of approximately 45.degree. or less with respect to a vertical axis. The flat side of the array includes a horizontal axis that is normal to the direction of tow. A drum on the ship stows the spreader bar assembles on flanges of the drum in successive layers and enables the array to be deployed.

Acoustic source array system for underwater operation

A pneumatic gun having a fast-acting sliding sleeve valve member reciprocating between two axial positions, first to open an exhaust port for the explosive release of gas from a pressurized charge chamber in a stationary housing while simultaneously closing a pressurized intake port to said chamber, and then to close said exhaust port while simultaneously opening said pressurized intake port for recharging said charge chamber, all for the purpose of generating repetitive trains of impulsive sounds at a rapid rate with increased efficiency. The sliding valve member comprises a sleeve and may include a piston in a cylinder within the housing. The sliding valve member has a sealing flange which forms a lip seal with a stationary annular mating surface of the gun to close an exhaust port. A wall of the charge chamber is provided with an intake port in communication with a source of high-pressure gas. The intake port is closed when the exhaust port is opened by the sliding action of the sleeve valve member, and is opened when the lip seal is formed to close the exhaust port. The sleeve is fitted with an annular cocking flange which is disposed in a cocking chamber supplied with high-pressure gas which exerts a continuous closing force against the cocking flange to form and maintain the lip seal except for those periods when the gun is actuated. A portion of one of the mating surfaces forming the lip seal is relieved to provide an activating chamber. High-pressure gas is provided selectively to the activating chamber generating in the activating chamber an opening force against the sealing flange, which force is larger than the closing force exerted against the cocking flange, thereby breaking the lip seal and permitting gas to acceleratively discharge from the charge chamber. In the piston embodiment, the acoustic output of the gun includes not only the explosive acceleration of gas from the exhaust port, but also the abrupt volume acceleration off the face of the piston.

Pneumatic gun for rapid repetitive acoustic firing

A pneumatic gun or air gun having a fast-acting sliding valve reciprocable between two axial positions to close or open intake and exhaust ports in a charge chamber in a housing. The sliding valve comprises a piston internal to the housing and may include a piston in a cylinder within and extending beyond the housing. The sliding valve has a sealing flange which forms a lip seal with an annular mating surface of the housing to close an exhaust port. Air accelerating from the gun may be radial from an equatorial exhaust port or may be axial from an end of the charge chamber. The charge chamber is provided with an intake port in selective communication with a source of pressurized gas, thereby to facilitate rapid charging rates. The intake port is closed when the exhaust port is opened by the sliding action of the valve member, and is opened when the lip seal is formed to close the exhaust port. The intake passages to the charge chamber are essentially unrestrictive of the flow of pressurized gas, thereby to facilitate rapid charging rates. The valve is fitted with an annular cocking flange which is disposed in a cocking chamber in the housing and is supplied with pressurized gas on one side to exert a continuous closing force to form and maintain the lip seal. Pressurized gas is provided selectively to the opposite side of the cocking flange to generate an opening force on the valve which is larger than the closing force, thereby breaking the lip seal and permitting gas to discharge suddenly from the charge chamber. In the axial end discharge embodiment, the acoustic output of the gun includes not only the explosive acceleration of gas from the exhaust port, but also the abrupt volume acceleration off the face of the piston.

Pneumatic gun for rapid repetitive firing

False target (reverberation, clutter, etc.) detection is suppressed in an echo ranging system (sonar or radar) in which target velocity and range are measured using a composite Doppler invariant-like signal having at least two segments, such as are present in a 'rooftop' or 'vee' HFM signal, such composite signal having an ambiguity function with two or more ridge lines of different slopes that intersect along the zero-velocity time axis. A bank of matched filters provides a distribution of outputs which has an ambiguity function-like character with intersecting pairs of ridge lines, the intersecting points of said pairs characterizing the range and velocity of the echo returns. This distribution is adjusted so that the intersecting ridge lines of each pair have equal and opposite slopes with respect to the time axis. In particular, fixed reverberators, which would have ridge lines intersecting on the zero-velocity time axis, would be symmetrical about this axis. A target with velocity v would present ridge lines intersecting along the v-velocity time axis and be symmetrical about that axis. Thus, the reverberation and the moving target would each have crossed ridge lines whose characteristic intersecting patterns would each exhibit symmetries, but about separate and distinct axes. False targets, including clutter and reverberation, are suppressed by subtracting from the adjusted output distribution, a replica thereof, folded (rotated) 180.degree. about a time axis containing the intersection of the ridge line pair corresponding to the false target which is to be suppressed. The rotation and subtraction of the replica from the adjusted distribution provides a set of outputs from which the real target velocity and range can be determined. The rotation-subtraction process can be implemented on an on-going basis to suppress a plurality or continuum of false targets and to achieve a desired width of a Doppler notch covering an arbitrary range of velocities.

Echo ranging system for detecting velocity and range of targets using

A water gun seismic source for use in underwater environments has a sleeve valve (100) for opening a jet aperture (37, 101) to enable jets of pressurized water to be emitted for the generation of a seismic signal. The water is pressurized by a drive piston (3) which is reciprocated to a cocked position for pressurizing the water for the jets. A compressed air operated cocking mechanism (4, 7, 8, 76 or 110-199 or 200-260) is coupled to the piston for cocking it. The cocking mechanism may utilize cocking piston (7) slideable on a shaft (4) connected to the drive piston (3) which cocking piston is returned to a position where any load due to such cocking piston is decoupled from the shaft. The sleeve valve (100) may be biased to close the jet aperture ports (101) by compressed air and opened with high timing resolution when the pressurized water held back by the sleeve valve is applied to actuate it (via 40, 41, 50 & 43). Compressed air may be released in the vicinity of the jet aperture ports to be entrained with the jets and assist in forming the vapor cavities which collapse to produce the seismic signal. When compressed air is used to help nucleate the vapor cavities it may also be applied, instead of the pressurized water, to the seat of the sleeve valve to actuate the sleeve valve and open the jet aperture ports.

Seismic source

In order to stress relieve exposed portions of plastic welds, and thereby reduce susceptibility of such welds to solvent-induced crazing and cracking, the welded parts are formed with flanges extending outwardly therefrom. These flanges are at least partially joined during welding, their adjoining surfaces providing at least a portion of the welded joint. After welding, the flanges are compressed in a direction transverse to their adjoining welded surfaces, the compression being of sufficient magnitude to exceed the yield strength of the flanges, thereby relieving stresses in the exposed portion of the welds. The flanges may be sheared, as by a blade which provides both transverse compressive forces and compressive forces in the direction of the adjoining welded surfaces. The flanges may be sheared through, so as to enable the sheared off end to be removed, or the shearing may penetrate only through the weld zone, providing a notch, but leaving the flanges in place. The compressed and/or sheared flanges provide an exposed portion of the welds in which tensile stresses are relieved, reducing susceptibility to solvent-induced crazing or cracking, and thereby edge sealing the welds.

Apparatus for stress relief and edge sealing of welded joints in plastic

A hydroacoustic transducer for generating and applying acoustic energy to a load coupling structure has a hydroacoustic amplifier with a driver stage and a power stage. The power stage includes a valve, which obtains high power conversion efficiency by operating to switch the flow of pressurized hydraulic liquid on and off thereby providing a switching amplifier which presents a pressure source of acoustic energy. This source is connected to a load coupling structure by way of an acoustic transformer and an inertive element in series with the source. The inertive element is provided by a liquid-filled bore and is terminated at its input end by the larger area of a stepped piston which provides the acoustic transformer. The smaller area of the stepped piston is in hydraulic communication with the power stage of the hydroacoustic amplifier. The series combination of the transformer and the inertive element resonates with the load coupling structure and provides a band pass frequency response characteristic with the load coupling structure. The hydraulic transformer reduces the input acoustic pressure levels from the amplifier, which are then raised again by the inertive element in the series tuned circuit including the inertive element and the load coupling structure, thereby allowing operation at pressure levels which avoid cavitation in the liquid filled elements of the apparatus as well as providing impedance matching between the hydroacoustic amplifier source and the load. The inertance of the inertive element may be varied with variation in frequency of the energy generated by the amplifier (over frequency sweeps) to maintain optimum tuning of the structure.

Hydroacoustic apparatus

In order to stress relieve exposed portions of plastic welds, and thereby reduce susceptability of such welds to solvent-induced crazing and cracking, the welded parts are formed with flanges extending outwardly therefrom. These flanges are at least partially joined during welding, their adjoining surfaces providing at least a portion of the welded joint. After welding, the flanges are compressed in a direction transverse to their adjoining welded surfaces, the compression being of sufficient magnitude to exceed the yield strength of the flanges, thereby relieving stresses in the exposed portion of the welds. The flanges may be sheared, as by a blade which provides both transverse compressive forces and compressive forces in the direction of the adjoining welded surfaces. The flanges may be sheared through, so as to enable the sheared off end to be removed, or the shearing may penetrate only through the weld zone, providing a notch, but leaving the flanges in place. The compressed and/or sheared flanges provide an exposed portion of the welds in which tensile stresses are relieved, reducing susceptability to solvent-induced crazing or cracking, and thereby edge sealing the welds.

Stress relief and edge sealing of welded joints in plastics parts

A seismic source drives one or more jets of high velocity water into an underwater environment and then terminates the jets by means of a valve member, the motion of which is controlled to obtain precisely timed high energy seismic pulses to provide reflected signals from which high resolution seismograms may be obtained when the signals are processed.

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Rochester, NY, United States of America

John V Bouyoucos