Abstract: A seismic source for generating seismic waves under water includes an operating head having an operating chamber, a cushion chamber, and discharge ports, a firing chamber attached to the operating head, the firing chamber configured to hold compressed air to be discharged through the discharge ports, and a shuttle assembly having a shaft located within the operating head and configured to prevent the compressed air in the firing chamber to enter the discharge ports when in a close state, and to allow the compressed air in the firing chamber to be discharged through the discharge ports when in an open state. The shaft of the shuttle assembly which extends in both the operating chamber and the cushion chamber, has a channel having a varying depth.

Abstract: Disclosed are embodiments of a marine vibrator and methods of using. Embodiments of the marine vibrator may comprise a containment housing; a piston plate, wherein an internal volume of the marine vibrator is at least partially defined by the containment housing and the piston plate, the internal volume containing a first gas at a first gas pressure; a fixture coupled to the containment housing; a mechanical spring element coupled to the piston plate and the fixture; a driver coupled to the piston plate and the fixture, wherein the driver is configured to move the piston plate back and forth; and a compliance chamber in contact with the first gas, wherein the compliance chamber comprises a second gas at a second gas pressure.

Abstract: Devices capable of being disposed in a wellbore for outputting acoustical signals for monitoring downhole parameters are described. Receiving devices positioned remote from the devices and can receive the acoustical signals and determine the downhole parameters. The devices can output acoustical signals in response to fluid flow or otherwise.

Abstract: A method for generating acoustic waves under water includes actuating first and second pistons with an actuator system provided inside an enclosure of a source element, to generate a wave having a first frequency, and actuating the first and second pistons with a pressure mechanism attached to the enclosure, to control a pressure of a fluid inside the enclosure such that a pressure of the fluid is substantially equal to an ambient pressure of the enclosure. The enclosure has first and second openings and the first and second pistons are configured to close the first and second openings.

Abstract: A marine vibrator with improved seal is described. The marine vibrator includes a housing and piston within the housing for generating vibratory signals. The improved seal is comprised of a two-stage seal having a first seal disposed adjacent the water interface and a second seal disposed away from the water interface, thus improving the reliability of the marine vibrator.

Abstract: A very low frequency marine seismic source has a reservoir of water (47) feeding water to an aperture communicating with the surrounding water (13). The rate of water flow through the aperture is controlled by a rotor disc (11) and stator disc (9) having holes which overlap to a greater or lesser extent as the rotor rotates. The modulation of the flow of water produces a modulated pressure signal which is radiated into the surrounding water. The device is intended to produce acoustic signals over a band extending down to 0.5 Hz or lower.

Abstract: A marine vibratory sound source for producing swept or pulse coded signals in a body of water and within geological structures beneath a body of water, primarily for seismic exploration of the strata beneath the bottom of the water. More particularly, a high power, servo controlled hydraulic, sound source that can readily be towed in water, towed along the bottom surface under the water or be used in a stationary position on the bottom surface under the water.

Abstract: A sound source includes a bubble configured to be filled with a gas. The sound source also includes an actuator configured to perturb the gas within the bubble by changing the volume of the gas without adding gas to or removing gas from the bubble. The sound source also includes a processing circuit configured to provide a control signal to the actuator to cause the actuator to perturb the gas within the bubble at a frequency defined by the control signal.

Abstract: A low frequency sound source has a radiating piston (3) of the order of a few meters across backed by a gas spring (13, 15) containing a fixed mass of gas. The gas pressure in the spring is kept at levels for which the natural frequency of the piston (3) loaded by the fluid (41) lies in the seismic band and may be as low as 0.5 Hz. The piston (3) is given an initial displacement and begins to oscillate. Its oscillations are sustained by an actuator (27, 29) whose drive signal is derived from the velocity of the piston (5) via a velocity or displacement sensor. The sound source is caused to perform a frequency sweep by gradually compressing the gas in the gas spring (13, 15) so that the spring becomes stiffer both because of the rising pressure and because of the reducing length of the gas spring spaces (13, 15). This double effect allows large changes in stiffness to be produced and hence allows the source to operate over at least three octaves of frequency.

Abstract: A bottom hole assembly is configured with a drill bit section connected to a pulse generation section. The pulse generation section includes a relatively long external housing, the particular housing length being selected for the particular drilling location. The long external housing is positioned closely adjacent to the borehole sidewalls to thereby create a high speed flow course between the external walls of the housing and the borehole sidewalls. The long external housing includes a valve cartridge assembly and optionally a shock sub decoupler. While in operation, the valve cartridge assembly continuously cycles and uses downhole pressure to thereby generate seismic signal pulses that propagate to geophones or other similar sensors on the surface. The amount of bypass allowed through the valve assembly is selectable in combination with the long external housing length and width to achieve the desired pulse characteristics.

Abstract: A marine vibratory sound source for producing swept or pulse coded signals in a body of water and within geological structures beneath a body of water, primarily for seismic exploration of the strata beneath the bottom of the water. More particularly, a high power, servo controlled hydraulic, sound source that can readily be towed in water, towed along the bottom surface under the water or be used in a stationary position on the bottom surface under the water.

Abstract: A forward and aft open-ended, towed underwater acoustic source having a hollow with a plurality of wires disposed in parallel across one or both of the end openings. In operation, water flows around the wires and proceeds through the hollow body, exiting the aft open end of the body. The tensioned wires are situated normal to the direction of flow in order to cause production of Strouhal vibration frequencies due to the vortex shedding action of the water flow behind the wires. The source transmits broadband acoustic energy without requiring heavy transducers.

Abstract: An active sonar system for detecting objects in water includes: a transmitter capable of generating and transmitting an acoustic signal having acoustic pressure pulses; a cable extending from the transmitter into the water, the cable including a hose filled with hydraulic fluid receiving the acoustic pressure pulses from the transmitter, a water blocking layer and cable wire; and a winch assembly including a winch drum for deploying and retrieving the cable into and out of water. A flattened hydraulic chamber section of the hose is secured within the winch drum with acoustic transducers mounted on either side of the flattened chamber section, so that the acoustic transducers act as pistons to generate acoustic pressure onto the hydraulic fluid for generation along a length of the cable.

Abstract: A sound source includes a tubular resonator configured to be filled with a gas. The exterior of the resonator includes rigid and elastomeric portions. The interior of the resonator includes a first volume and a second volume. The volumes are separated by a rigid tubular wall containing at least one orifice. The at least one orifice enables a flow of gas between the volumes. The resonator also includes at least one rigid tubular member configured to move along the rigid tubular wall. The position of the at least one rigid tubular member regulates at least one dimension of the path between the volumes. The sound source also includes a volume velocity actuator disposed within the resonator. The sound source also includes a processing circuit configured to provide a control signal to cause the volume velocity actuator to perturb the gas within the resonator at a defined frequency.

Abstract: A marine vibratory sound source for producing swept or pulse coded signals in a body of water and within geological structures beneath a body of water, primarily for seismic exploration of the strata beneath the bottom of the water. More particularly, a high power, servo controlled hydraulic, sound source that can readily be towed in water, towed along the bottom surface under the water or be used in a stationary position on the bottom surface under the water.

Abstract: A seismic energy source includes an inlet aperture and an inlet pipe in fluid communication with an outlet of the inlet aperture at an inlet end of the inlet pipe. The inlet pipe is in fluid communication with an accumulator at an outlet end of the inlet pipe. An outlet pipe is in fluid communication with the accumulator at an inlet end of the outlet pipe and is connected to an outlet valve at an outlet end of the outlet pipe. The outlet valve is actuated by fluid pressure in the outlet pipe. An actuation pressure of the valve, and diameter, length and material properties of the outlet pipe are selected to cause a reflected water pressure wave resulting from closure of the valve to travel within the outlet pipe at a selected velocity. Motion of the seismic source through the water provides water pressure to operate the source.

Abstract: A sound source includes a tubular resonator configured to be filled with a gas. The exterior of the resonator includes rigid and elastomeric portions. The interior of the resonator includes a first volume and a second volume. The volumes are separated by a rigid tubular wall containing at least one orifice. The at least one orifice enables a flow of gas between the volumes. The resonator also includes at least one rigid tubular member configured to move along the rigid tubular wall. The position of the at least one rigid tubular member regulates at least one dimension of the path between the volumes. The sound source also includes a volume velocity actuator disposed within the resonator. The sound source also includes a processing circuit configured to provide a control signal to cause the volume velocity actuator to perturb the gas within the resonator at a defined frequency.

Abstract: A sound source comprises a bubble configured to be filled with a gas, an actuator configured to perturb the gas within the bubble, and a processing circuit configured to provide a control signal to the actuator to cause the actuator to perturb the gas within the bubble at a frequency defined by the control signal.

Abstract: A marine vibrator with improved seal is described. The marine vibrator includes a housing and piston within the housing for generating vibratory signals. The improved seal is comprised of a two-stage seal having a first seal disposed adjacent the water interface and a second seal disposed away from the water interface, thus improving the reliability of the marine vibrator.

Abstract: In a measuring while drilling or similar system, a pressure balance drive cylinder exhaust valve is driven by a toggling sense piston. Reset of the sense piston creates a pressure balance across the exhaust valve such that, as the pressure within the drive cylinder regeneratively increases, this pressure is applied to both sides of the exhaust valve. The pressure balance thus created greatly reduces the force necessary to close the exhaust valve. Once the sense piston is driven past the toggle allowing the drive cylinder pressure to have an offset pressure equal to the downstream main valve pressure, the drive cylinder forces the exhaust valve open thus decreasing the drive cylinder pressure. The pressure reduction allows the sense piston to reset, thereby restarting the process.

Abstract: A low frequency sound source has a radiating piston (3) of the order of a few metres across backed by a gas spring (13, 15) containing a fixed mass of gas. The gas pressure in the spring is kept at levels for which the natural frequency of the piston (3) loaded by the fluid (41) lies in the seismic band and may be as low as 0.5 Hz. The piston (3) is given an initial displacement and begins to oscillate. Its oscillations are sustained by an actuator (27, 29) whose drive signal is derived from the velocity of the piston (5) via a velocity or displacement sensor. The sound source is caused to perform a frequency sweep by gradually compressing the gas in the gas spring (13, 15) so that the spring becomes stiffer both because of the rising pressure and because of the reducing length of the gas spring spaces (13, 15). This double effect allows large changes in stiffness to be produced and hence allows the source to operate over at least three octaves of frequency.

Abstract: A sweep generator is employed to generate a sweep to be used by a seismic vibrator device for generating a desired target output spectrum, wherein the frequency sweep is designed so as to comply with one or more constraints imposed by the seismic vibrator device and/or imposed by the environment in which the device is to be used. In one embodiment, a sweep generator determines a sweep for achieving a desired target output spectrum by a given seismic vibrator device in compliance with at least a pump flow constraint imposed by the seismic vibrator device. In another embodiment, a sweep generator determines a sweep for achieving a desired target output spectrum by a given seismic vibrator device in compliance with all of multiple operational constraints of the seismic vibrator device, such as both mass displacement and pump flow constraints. Environmental constraints may also be accounted for in certain embodiments.

Abstract: A solid metallic piston of a fluidborne sound projector is provided with a plurality of parallel spaced fluid passages extending between opposite axial end faces of the piston so as to equalize fluid pressures exerted thereon within a chamber enclosed within an end portion of a conduit having an end wall attached thereto through which a solid piston rod extends from the piston to an acoustical power source from which acoustical energy is mechanically transmitted as displacing forces applied to one of the axial end faces of the piston. Displacement of the piston within the chamber is limited in one axial direction by abutment of the rear end face thereof with the conduit end wall and in the other axial direction by abutment of a larger diameter section of the piston with a forward stop on an annular seal fixed to the conduit end portion, through which a smaller diameter section of the piston extends from the larger diameter section.

Abstract: An acoustic fluid machine has an acoustic resonator and a piston reciprocated by an actuator at the base of the acoustic resonator. A valve device is provided on the upper end of the acoustic resonator. External air is introduced into the acoustic resonator through the valve device. The piston has through-holes, through which front space communicates with rear space thereby reducing load applied onto the piston.

Abstract: An acoustic projector device having a piston exposed to pressure balanced air and water in an acoustically ideal position thereof within a piston chamber enclosing sleeve disposed in an outer housing to which deaerating water is selectively supplied in surrounding relation to the piston chamber sleeve while in communication with one side of the piston through axial slots in the sleeve uncovered by displacement of the piston from said acoustically ideal position.

Abstract: Streamlined, towable, marine seismic energy vibrator for creating intense swept-frequency and pulse-coded seismic signals in a body of water has a sleek, fish-like configuration designed for towing with minimum drag. The vibrator has a streamlined hollow towing head and a streamlined hollow tail head mounted onto front and rear of a long cylindrical tubular wall which is modular, comprising cylinder sections joined in end-to-end axial alignment. Within this long tubular cylinder wall is an axially vibratable multi-piston assembly having a plurality of pistons on a long piston rod. One piston is positioned in each of the cylinder chambers. These chambers hive multiple ports opening out through the long cylindrical wall. An elongated circular cylindrical elastomeric bladder forms a water-filled bladder chamber encircling the wall.

Abstract: A fluidborne projector of sound derived from an electro-mechanical noise source translates acoustical energy through a piston subjected to balanced pressures of gas and liquid to enabled dynamic displacement thereof. Such displacement of the piston to a static position is regulated by controlled pressurization of gas, mechanically limited to prevent damage from changing pressures exerted on the piston.

Abstract: A method and device for generating a high amplitude sound wave is provided. The device includes a housing having an open end. A piston is slidably disposed in the open end of the housing and forms a chamber for holding a pressurized liquid. The pressurized liquid acts on the piston to move the piston relative to the housing. A latch is operable to fix the piston relative to the housing and to release the piston. Upon release of the latch, the piston moves relative to the housing to generate the sound wave. In the method of the present invention, a piston is fixed relative to a housing to form a chamber between the housing and the piston. The chamber is filled with a pressurized fluid and the piston is released to allow the pressurized fluid move the piston relative to the housing and generate the sound wave.

Abstract: An apparatus for generating acoustic source energy in a liquid medium. A slotted cylinder has an interior volume filled with a fluid. An actuator selectively pressurizes the fluid to expand the slotted cylinder. Movement of the slotted cylinder due to expansion and contraction generates a pressure pulse in the liquid medium to create acoustic source energy. The device provides an acoustic source for marine seismic operations and for use downhole in a borehole.

Abstract: An impulsive snap-through acoustic pulse generator may be used to generate n acoustic pulse in an aqueous environment without gas bubbles. The impulsive snap-through acoustic pulse generator includes a support structure having an open end; a resilient shell mounted to the support structure to define a chamber, and a gas vent in fluid communication with the chamber through which a gas passes for changing the pressure in the chamber so that the resilient shell transitions from a first stable state to a second stable state, thereby generating an acoustic pulse.

Abstract: The invention provides apparatus for shaking structures such as fins in a fluid agitator, shaking tables, shaking screens, conveyors, or the walls of bins or hoppers. The apparatus is driven by a hydraulic driving system in which high pressure pulses are generated by repeatedly creating water hammer within a conduit. The high pressure pulses are directed to a chamber where they act against a wall of the chamber to periodically push on the structure. Preferably, the structure is spring-like so that after a high pressure pulse has passed the wall of the chamber is returned to its equilibrium position. In one embodiment of the invention a water hammer pressure pulse is directed into a reinforced hose in contact with a surface to be vibrated. The high pressure pulse causes the hose to expand and move the surface to be vibrated. Water hammer pulses are generated periodically so that the surface is maintained in continuous vibration.

Abstract: A method and apparatus are disclosed for generating intense acoustic pulses by means of the water hammer effect. The method involves generating a water hammer in a conduit by suddenly interrupting a high velocity flow of fluid through the conduit. The kinetic energy of the fluid flowing in the conduit is converted into a high pressure pulse which propagates along the conduit away from the point where the fluid flow was interrupted. The high pressure pulse deforms the wall of the conduit so as to radiate acoustic energy away from the conduit into a fluid medium surrounding the conduit. The relative amount of energy dissipated in the form of mass flow in the surrounding fluid and acoustic energy in the surrounding fluid can be adjusted by changing the characteristics of the conduit wall. The direction in which acoustic energy is radiated into the fluid medium surrounding the conduit can be set by making the conduit wall asymmetrical or by bending the conduit.

Abstract: Gas-operated apparatus (2) for making a noise underwater, comprising a body (4), a diaphragm (6) which extends over the body (4) to define a chamber (8) between the body (4) and the diaphragm (6), a gas inlet nozzle (10) which extends into the chamber (8) and which engages an inner surface (12) of the diaphragm (6), and gas outlet means (14) for enabling gas in the chamber (8) to leave the chamber (8), the diaphragm (6) being made of an elastic material, the diaphragm (6) being such that it has an outer surface (16) which is in contact with a liquid, and the apparatus (2) being such that in use gas under pressure passes through gas inlet nozzle (10) and causes the diaphragm (6) to expand and collapse over a region of the diaphragm (6) that is in contact with the gas inlet nozzle (10) thereby to create noise which is adapted for optimum underwater transmission due to the diaphragm (6) being in contact with the liquid.

Abstract: An acoustic wave generator for telemetering signals through a drillstem comprises a sub interposed in the drillstem with a central mandrel and a piston mass disposed in sleeved relationship around the mandrel and reciprocable by hydraulic pressure fluid to impose reaction forces on the mandrel and the drillstring at selected frequencies to transmit acoustic waves through the drillstring. A control system for operating the generator includes a hydraulic pump, a control valve and a frequency control circuit which operates the control valve to effect reciprocation of the piston mass at selected frequencies for transmitting serial data from the control system through the drillstring to a receiving system. The generator is coaxially arranged in the drillstring and is operable to generate high-energy acoustic wave signals for propagation through relatively long drillstrings.

Abstract: The method and apparatus for providing elliptical polarized shear waves in a marine environment in which a shear wave source penetrates the surface sediment of a water bottom includes dual actuator/reaction mass system mounted inside a structural ring of a conical housing section. A cross shaped structure at the top of the apparatus serves as a passive reaction mass and as a moment arm support for reversibly motor driven propellers enclosed in shrouds at the outer ends of the cross shaped structure. A thruster system provides dynamic positioning. The cross shaped structure and housing section are connected by a structurally stiff member, such as a vertical tube. Pistons provide actuation of two reaction masses located within the housing structure, and the motions of the reaction masses generate shear waves which propagate in the subsurface formations.

Abstract: A piezoelectric seismic vibrator is disclosed which utilizes a hydraulic system to amplify the longitudinal displacement which results from the application of a voltage to a stack of piezoelectric elements. In each disclosed embodiment of the present invention, a stack of piezoelectric elements is mounted so as to bear upon a power piston which in turn acts upon a high bulk modulus substantially incompressible body of fluid, such as mercury. A drive piston is provided having a cross-sectional area which is smaller than the area of the power piston and the pressure within the fluid system acts to amplify the longitudinal displacement of the piezoelectric elements. The movement of the drive piston is then coupled mechanically or fluidically to the earth to generate seismic waves therein. In one depicted embodiment of the present invention each stack of piezoelectric elements is disposed within a fluid filled chamber which is pressurized by means of communication with the borehole fluids.

Abstract: A shipboard support stand for a marine vibrator of the type having characteristic revolutional shape about the vertical axis and a lower concentric guide ring surface which consists of a support ring of circumfery generally equal to the circumference of the vibrator supported by plural vertical supports above the ship's deck, and which further includes a reduced diameter locating ring secured concentrically and at lower elevation from the support ring such that the vibrator can be supported on the support ring with the vibrator guide ring closely retained within the locating ring to stow the vibrator securely.

Abstract: A seismic source marine vibrator having compound hydraulic cylinders for high and low frequencies is used to generate both low frequency and high frequency acoustic pulses. Low frequency pulses are generated by operating a low frequency radiating surface and a high frequency radiating surface simultaneously. High frequency pulses are generated by operating the high frequency radiating surface alone.

Abstract: A multiple frequency range hydraulic actuator includes a low frequency cylinder with a low frequency actuator piston within. The low frequency piston operates as a high frequency cylinder having a high frequency piston within. The low frequency piston, and high frequency piston operate in conjunction to generate low frequency movement. The high frequency piston operates independently to generate high frequency movement.

Abstract: A marine seismic vibrator includes a housing having first and second housing portions defining an internal chamber therebetween. A hydraulic cylinder or other energizing device is connected between the first and second housing portions. The first and second housing portions are maintained in a spaced apart, non-contacting relationship. Relative motion between the first and second housing portions is provided by the hydraulic cylinder in order to generate acoustic waves in a surrounding body of water. An annular flexible seal construction is connected between the first and second housing portions for isolating the internal chamber from the surrounding body of water. This seal construction includes first and second flexible web portions sealingly connected to the first and second housing portions. A rigid hoop is connected between the first and second web portions for supporting the seal against pressure differentials between the internal chamber and the surrounding body of water.

Abstract: A seismic energy source provides a bias pressure and oscillating pressure force on a piston mounted transversely to the major axis of the well bore and in pressure contact with the wall of the well bore. A seismographic energy wave is generated in the surrounding earth by oscillating the pressure of the piston against the well wall. This apparatus uses the pressure of ambient fluid in the well bore to reduce the power required to provide pressure contact and to oscillate the piston against the wall.

Abstract: The method and apparatus for generating seismic vibrations in a liquid includes an electronically controlled, hydraulically powered generator that includes a piston assembly reciprocally mounted on a cylindrical post in a generator housing. The control apparatus includes a control valve that is located very close to the piston assembly thereby reducing the volume of the passageways extending to the piston assembly so that the cyclic rate of the piston assembly can be very rigid and can be changed accurately and quickly. An extended life is provided by releasing the high pressure fluid driving the piston assembly prior to impact between the piston assembly and the post and by providing a trapped volume of fluid in the chamber to damp the movement of the piston assembly toward the post.

Abstract: Described is a method of driving a seismic vibrator with a control signal to produce an output signal having minimized harmonic distortion. The method includes the steps of producing a plurality a harmonic distortion signals related to a fundamental frequency of the control signal. The phase and amplitude of said harmonic distortion signal is varied to produce with the vibrator suites of variations of the distortion signal. From among suites of variations there is selected that harmonic distortion signal having phase and amplitude values which produce a minimum value in harmonic distortion signal amplitude. The steps are repeated for different fundamental frequencies and the selected signals are summed with their related fundamental frequencies to produce a vibrator sweep control signal. The seismic vibrator is driven with the control signal to produce an output in which harmonic distortion is significantly attenuated.

Abstract: An underwater vibrator is specifically adapted for generating a shear wave in a seabed and includes a frame; locomotion apparatus attached to the frame for moving the vibrator over the seabed; and cable means connected between a surface support vessel and the vibrator. The vibrator also includes buoyancy and apparatus for selectively controlling the buoyancy along with apparatus for selectively engaging the seabed with the vibrator. Apparatus is also carried by the vibrator for viewing the location of the vibrator under the water which includes lights and television equipment.

Abstract: 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.

Abstract: A device for generating sound pulses in a well by a mobile mass striking against a target element integral with an elongate body anchored in a well by retractable shoes actuated by hydraulic cylinders. The mobile mass which slides in a first chamber in the body is moved away by a piston moving in a second chamber of the body and intermittently locked in the moved away position by a valve. The piston, the valve and also the hydraulic cylinders acting on the anchorage shoes are actuated by a hydraulic system which may be remote controlled from the surface.

Abstract: An apparatus for incremental cylinder length control in a hydraulic vibrator of the type having a reaction mass with a cylinder bore disposed therein, first and second end sleeves disposed in sealed movable position in the ends of the cylinder, a piston rod sealed and slidably disposed through the first and second sleeves with a piston attached to the piston rods where the improvement comprises threading the ends of the cylinder bore and forming mating threads on the first and second sleeves with means for rotating the sleeves with respect to the cylinder so that the sleeves move toward or away from the piston thereby reducing the volume of hydraulic oil between the end of the piston and the end sleeves.

Abstract: Mounting structure for a marine seismic vibrator comprising at least three acoustic isolators equally spaced apart about an upper housing of the vibrator. Each of the isolators comprises a pair of spaced mounting pads mechanically secured to the housing. A U-shaped bracket having a base and depending spaced leg portions is attached to the mounting pads by way of a low-pass acoustic filter. A rectangular shaped bracket has a base, a top and a pair of spaced vertical sidewalls. The rectangular shaped bracket is located between the spaced leg portions of the U-shaped bracket and a resilient means is mounted between the bases of the U-shaped bracket and the rectangular bracket to provide a high-pass acoustic filter. Means mechanically connected to the top of the rectangular brackets to the tops of the mechanical brackets secure all the isolators to a common point at the center of the housing.

Abstract: The invention relates to a compact tunable subsea seismic source. The source has multiple seismic radiating plates placed symmetrically about a central housing which contains a hydraulic actuating system. The source is towed to optimize the amount of energy applied to the surrounding water.

Abstract: The disclosed device is a marine seismic source which produces a varying FM signal often in the 10-100 Hertz region of the spectrum. The seismic source uses stiff oscillating radiators to create a signal in the water. These radiators are actuated by hydraulic cylinders which are in hydraulic communication with hydraulic or oleo-pneumatic variable devices acting as springs with a variable spring rate. Variation of the spring rate as a function of the frequency permits the device to be tuned for maximum power output.