Abstract: A staggered vertical marine seismic source contains upper and lower arrays (10, 11) of emitters of seismic energy (S11, S12; S21, S22). The upper array (10) is horizontally displaced relative to the lower array (11). The source is used in a marine seismic surveying arrangement that has means for moving the source and at least one seismic receiver. In use, the source is moved through the water in a direction parallel to the direction in which the two arrays are displaced. The arrays (10, 11) are fired sequentially, and the time delay between the firing of the first-fired array and firing of the second-fired array is chosen such that each seismic emitter in one array is fired at the same x- and y-co-ordinates as the corresponding emitter in the other array. The seismic wavefields generated by firing the two arrays are thus generated at the same x- and y-co-ordinates, but at different depths.

Abstract: An in-water distributed control system for use in marine seismic survey. The system includes a shipboard interface and power supply coupled to an in-water subsystem via a high bandwidth communication link. The in-water subsystem includes a remote control module for generating firing commands based on synchronizing and position parameters transmitted by the interface. The remote control module transmits power, data, and commands to a plurality of gun control modules. Each gun control module operates an air gun. An individually addressable remote cut-off valve controls air to each air gun. Depth and pressure at the gun control module is sensed by at least one DT/PT module. An optional expansion unit provides additional DT/PT capability.

Abstract: 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.

Abstract: A graphical user interface (GUI) and control system for controlling and testing an acoustic source. The control system includes real-time data processing of individual source near-field measured signatures and synthesis of array far-field signatures. The control system determines individual source out-of-specification conditions and computes far-field signatures based on an array configuration and, when applicable, excluding failed sources. Source, array, and troubleshooting information are presented to a user in real-time over a GUI monitor to allow informed decision-making regarding continued and/or modified survey operations and operational parameters.

Abstract: Disclosed herein is a single point seismic system comprising an array of air guns disposed within a frame. The array includes a cluster of air guns on one of its ends and a reduction in chamber size of the air guns along the length of the array. On the end of the array opposite the cluster the array can comprise a series of air guns whose chamber size is an order of magnitude less than the chamber size of the guns comprising the cluster. The middle of the array can comprise a series of air guns whose respective chamber volumes differ by an order of magnitude. The frame of the present invention is generally wholly submerged during operation and does not interfere with the seismic signal produced by the firing of the air guns.

Abstract: 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.

Abstract: A seismic signaling apparatus (100) and method for enhancing the repeatability of the generated seismic signals are disclosed. The seismic signaling apparatus (100) includes a support frame (102) having an air-gun array (114) operably mounted thereto. The air-gun array (114) includes a plurality of air-guns (118, 120, 122) that are positioned such that a tapered, heavy centered, point source seismic signal is generated upon firing of the air-gun array (114). Shock absorbing members (124) are attached to adjacent air-guns (118, 120, 122) in order to absorb the force generated by the firing of the air-gun array (114). In particular, the shock absorbing members (124) absorb the forces associated with air-gun recoil to minimize the movement of the air-guns (118, 120, 122) relative to each other and the support frame (102), thereby stabilizing the air-gun array (114) and enhancing the repeatability of the generated seismic signals.

Abstract: A marine seismic source consists of one or more airguns (1) suspended from a float (2). A supply harness (5) is provided to supply compressed air and electrical control signals to the airguns. The airgun is mounted such that the harness (5) is below the point at which air is emitting from the airgun (1). This means that bubbles of air that rise from the airgun when it is fired do not impact on the harness and so cannot damage the harness.

Abstract: A marine acoustic source system has relativley densely packed energy sources arrayed in a tandem-like fashion along a horizontal plane. Preferably, a longitudinal axis of each source lies orthogonal to a pre-determined towing direction. The system includes protective tubes that encloses supply lines and auxiliary equipment, and a harness. The harness provides the primary mechanical connection for towing the sources through the water. To minimize bending of the supply lines, connectors having angular portions connect the sources to the supply lines. Further, the sources can be arranged such that source connection interfaces for receiving power, hydraulic fluid, or data point alternately in opposing directions. During use, the sources, e.g., air guns, are supported at a predetermined depth beneath the water's surface by a floatation buoy. Upon activation, the sources of a cluster each release individual air bubbles into the water.

Abstract: A sound mitigation system and method reduce the transmission of acoustic output from explosions underwater. The system is submerged to bottom terrain of a body of water and has at a series of gas-generating devices providing volumes of gas that are fed to refractory heat resistant tubing assemblies and flexible general tubing assemblies. The heat resistant and general tubing assemblies extend between adjacent gas generating devices and are provided with at least one row of holes to vent bubbles of gas and form a virtually continuous curtain of bubbles rising to the surface of the water between detonating explosives and areas of interest. The curtain of bubbles mitigates the effects of the explosions on marine mammals and endangered, threatened, or protected species within an area adjacent to the explosions.

Abstract: The present invention provides a pressure-balanced inertial valve assembly for use in marine seismic energy sources such as air guns. The valve includes a poppet having a first seal and a second seal. A pressure chamber containing a fluid under pressure communicating with the first and second seals to substantially balance the pressure across the seals. An inertial mass is coupled to the poppet. A coil assembly is disposed about the inertial mass. A central guide pin provides guided movement for axial translation.

Abstract: The present invention provides a pressure-balanced inertial valve assembly for use in marine seismic energy sources such as air guns. The valve includes a poppet having a first seal and a second seal. A pressure chamber containing a fluid under pressure communicating with the first and second seals to substantially balance the pressure across the seals. An inertial mass is coupled to the poppet. A coil assembly is disposed about the inertial mass. A central guide pin provides guided movement for axial translation.

Abstract: The invention describes an air gun for use in a marine seismic system. The air gun includes a gun body and shuttle that define a chamber containing a compressed supply of gas. The air gun is further designed to release the compressed gas so that the release time or gun fire time is monitored with sufficient accuracy. The fire time is measured by a timing coil that determines the location of the air gun shuttle by sensing a magnet disposed on the shuttle. The timing coil is designed to eliminate interference caused by magnetic flux generated by the actuation of an air gun solenoid valve.

Abstract: The invention describes an air gun for use in a marine seismic system. The air gun includes a gun body and shuttle that define a chamber containing a compressed supply of gas. The air gun is further designed to release the compressed gas so that the release time or gun fire time is monitored with sufficient accuracy. The fire time is measured by a timing coil that determines the location of the air gun shuttle by sensing a magnet disposed on the shuttle. The timing coil is designed to eliminate interference caused by magnetic flux generated by the actuation of an air gun solenoid valve.

Abstract: In a cable with a pneumatic hose, a sheath (9) encloses the hose and conductor elements (6) which are disposed between the sheath (9) and the hose. A layer of compressible material (5) is disposed between the conductor elements (6) and the hose.

Abstract: A valving system is disclosed which generally comprises a body including an inlet and an outlet where the inlet is disposed in fluid communication with a fluid flow passage and the outlet is disposed in fluid communication with a pressurized fluid member, the body further defining an internal bore in which is slidably disposed a piston moveable between a first and a second position such that fluid communication between the fluid flow passage and the fluid flow member is established when the piston is disposed in the first position but not in the second position, an apparatus and to move the piston from the first position to the second position so as to interrupt fluid flow from the fluid flow passage to the fluid member.

Abstract: 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.

Abstract: A well tool in accordance with the invention comprises an attenuation device which attenuates tube waves associated with an elastic wave emission and/or reception set (1, 12). The attenuation device comprises a bubble generator (2) which releases into the well a gas not readily soluble in the well fluid, slightly overpressured in relation to the hydrostatic pressure, in the form of calibrated bubbles which greatly attenuate the parasitic tube waves. The attenuation device is placed above or below the elastic wave emission and/or reception set having a plurality of pickups whose signals are acquired by a local electronic module (14) and/or a source of elastic waves such as a vibrator. A bubble trap (17) is preferably associated with the bubble generator (2) in order to limit the volume of gas to be generated in situ. The invention is applicable to VSP type seismic prospecting and acoustic logging.

Abstract: The method involves using an acoustic wave generating apparatus, such as an "air gun", which employs only a single gas or single gas mixture and which has a gas pressurizable chamber with an inlet for permitting pressurized gas to be introduced into the chamber and a closed outlet which can be opened rapidly to release pressurized gas from the chamber into a liquid to generate acoustic wave energy. Hydrogen and/or helium is/are used instead of air as the gas with the result that the strength and quality of the initial pulse of the generated wave energy is improved.

Abstract: A marine seismic cable system for marine surveying comprises an electrical conductor within a tubing for conveying compressed air and electricity between a seismic vessel and equipment such as air guns. The tubing resists elongation caused by water drag forces acting against the tubing exterior surface and provides a protective shield to the enclosed electrical conductor or conductor bundle. This combination uniquely conveys compressed air and electricity while significantly reducing the outside cable diameter to reduce the weight and drag forces acting on the cable system. The combination also permits repair and replacement of the tubing or electrical conductor independent of the other component.

Abstract: A method and apparatus for controlling the operation of a multiple-element marine seismic pulse generating source in rough sea surface conditions. The method first determines the shape of the path along which the elements are traveling at the point in time just before each element of the source is activated. Once the shape of the path is known, the relative vertical position of each element relative to a fixed reference is determined. Adjustments can then be entered into the firing times for each element such that the primary pressure peaks constructively interfere with one another. In a preferred embodiment, a plurality of inclinometers associated with the harness from which the devices are suspended provides a tilt angle measurement from which the shape of the path can be determined and the firing times adjusted accordingly.

Abstract: An acoustic generating system is described incorporating a bubble generator (1) for forming pressurised gas bubbles and directing the bubbles in a plume from an outlet (7), and a low frequency sound source (2) to apply a varying pressure to the base of the plume of bubbles to modulate (8) the plume of bubbles, whereby a source of low frequency sound waves is produced. A method for generating and transmitting a low frequency acoustic wave using is also described.

Abstract: An array system, which provides a unipolar acoustic impulse with a broad spectral response underwater, utilizes a vertical array of airgun or electrical spark sources whose individual peak source strengths are essentially constant over the array length, but whose individual source periods vary with depth. The array of sources produces in each instance a near-unipolar, impulsive signature with a broad pedestal-like spectrum. The system may be used for underwater object location and also for seismic exploration.

Abstract: 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.

Abstract: A wear ring assembly for an air gun includes a support ring having a receiving recess of a first length formed in a surface of an end of the support ring. An elastic ring is adjacent an end of the receiving recess. A wear ring seats in the receiving recess and is of a second length, greater than the first length, such that a portion of the wear ring overlaps the end of the support ring, thereby covering and deforming the elastic ring. The wear ring is formed of a thin, low-friction, wear-resistant plastic material having dimensions such that the wear ring does not plastically yield during installation into the receiving recess. Installation is accomplished by attaching a core tool adjacent the seal groove. The wear ring is installed with an expanding pusher tool, over the core tool and into the receiving recess.

Abstract: A seismic air gun includes a body, a main chamber, two ports, several air passageways, a shuttle, a return device, and a firing device. The main chamber is within the body. The two ports are in the main chamber. The ports lie along a common axis. The air passageways connect a high pressure air source to the return device, the main chamber, and the firing device. The shuttle slides along the common axis between an open position, in which the main chamber is open, and a closed position, in which the main chamber is closed. The return device biases the shuttle toward the closed position. The firing device causes the shuttle to move from the closed position to the open position whereby pressurized air is released simultaneously from the two ports and in opposite directions.

Abstract: 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.

Abstract: 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.

Abstract: For marine seismic surveying using an array of airguns towed behind a survey ship, wherein a common high pressure hoseline supplies compressed air to a multitude of airguns, a method, system and apparatus selectively shut off air flow to any airgun for stopping leakage of compressed air from the common supply line. Shutoff valves are employed with a respective valve being upstream of each airgun to enable selectively shutting off compressed air flow from the common supply line to any airgun for stopping loss of compressed air from the common line caused by leakage from a leaking component downstream from any valve, such as a ruptured feeder hoseline to an airgun. Each shutoff valve has a spring whose spring force biases open its valve. Simultaneous electrical energization of windings in all shutoff valves electromagnetically overcomes the spring force for simultaneously closing all valves.

Abstract: A sleeve air gun for releasing compressed air into water. The air gun housing has a chamber enclosed with an end cap. The end cap is engaged with the air gun housing with a retainer that is light weight and expedites the engagement and disengagement of the end cap and housing. The retainer can comprise a light weight ring that engages the housing and end cap. The retainer uniquely permits larger diameter air guns to be constructed without disproportionately increasing the weight of the air gun. The larger diameter air gun expedites the discharge of compressed air from the air gun, which maximizes the acoustic pulse generated in the water.

Abstract: An air gun for releasing compressed air into the environment. Two opposing shuttle valves selectively open ports to release compressed air more quickly from the air gun. A centering mechanism returns the first and second shuttle valves to the initial position. The centering mechanism can comprise a pressure compensation system or mechanical stop for positioning the first and second shuttles at the selected position.

Abstract: Seismic airgun arrangement for attenuating unwanted oscillations in the emitted signal. The airgun has one or more outlet ports (9) for exhausting air in a generally radial direction from a central axis of the airgun (10), and a perforated screen (20) of plate material is provided around the airgun for the attenuation mentioned. The volume generally delimited within the screen (20) is significantly smaller than the maximum bubble size which is normally generated by the airgun (10). The screen (20) has an open side or end (20A) at a part of the screen that is adapted to face at least partially downward in the normal operative position of the airgun (10). At least edge portions of the screen along the open side or end (20A) are located substantially directed opposite the outlet port or ports (9).

Abstract: This invention is a seismic source system for marine surveying using a small diameter hose bundle containing an electrical cable disposed within an air hose which is reinforced with torque-balanced layers of armor components and protective jacket and connected to a termination assembly at one end for connection to an electrical power supply, pressurized air supply and control system and connected to another termination assembly at the other end for connection to an air gun subarray comprising multiple air guns.

Abstract: A device for securing two or more seismic energy sources at fixed relative positions during firing of the sources consists of a rigid framework comprising end frames and intermediate bars. In order to provide an extremely light but at the same time completely rigid framework, the seismic energy sources are used as longitudinal bars between the end elements.

Abstract: A seismic source apparatus 10 includes body 12, cap 22, actuator 24, and shuttle 26. Body 12 includes a main chamber 14 that is formed therein and adapted to receive a charge of compressed air. Actuator 24 is preferably a solenoid actuated valve, capable of rapidly opening and closing in response to an electrical signal. Seismic source apparatus 10 includes a solenoid chamber orifice 38 that is positioned within a fill passage 34 to enable fluid communication between fill passage 34 and solenoid chamber 40. Solenoid chamber orifice 38 and solenoid chamber 40 are configured to provide a quick burst of high pressure air through actuator 24 when actuator 24 is opened in order to start the shuttle 26 in motion, while restricting the flow of air from main fill passage 34 and main chamber 14 into the actuator 24 so that the pressure in the main chamber 14 remains high enough to emit a suitable bubble, and so that shuttle 26 is not prevented from closing.

Abstract: A large-diameter, cylinder-shuttle airgun for seismic uses has a cylinder shuttle configured as a hollow, elongated cylinder body of revolution with an inwardly-facing cylinder guide surface and having two outwardly-extending, axially-spaced annular flanges. These two annular flanges are an operating flange at an upper end of the body of revolution and a firing flange at an intermediate region thereof. A cylinder skirt extends down below the firing flange, and the cylinder shuttle has an overall axial length L. The firing flange has a perimeter of outside diameter OD, and the ratio of L to OD is at least about 1 to 1. A cylinder housing of the airgun has a main inner cylinder structure encircled by the cylinder shuttle. This main inner cylinder structure may have an axial passageway of sufficient diameter for passing at least one compressed air hose and at least one multi-conductor electric cable axially therethrough.

Abstract: The present invention is directed to a method and apparatus for substantially suppressing the undesired recoil derivative from the explosive discharge of high pressure gas from an airgun while still providing for useful optimized pressure pulses.

Abstract: The invention provides an air gun responsive to a supply of compressed gas, which facilitates rapid acceleration of a shuttle member to selectively actuate the air gun. The air gun includes a primary firing chamber which receives compressed gas in order to move the shuttle valve member to its full open position. The air gun also includes an initial acceleration chamber which provides an additional piston surface during the initial movement of the shuttle valve member so as to optimumly accelerate the valve member. This results in improved firing time repeatability.

Abstract: An acoustic emission system for seismic surveying at sea, for the purpose of emitting a soundwave in a given direction, the system comprising firstly a plurality of immersed sources mechanically connected to at least one float means and secondly a control circuit for controlling said sources and comprising a plurality of delay means suitable for applying respective phase delays to each of the sources, said delays being defined by a nominal phase law associated with said given emission direction. According to the invention, the system also includes at least two attitude sensors providing signals representative of the absolute position of at least two of said sources to correction means of said control circuit, said correction means providing each of said delay means with a signal for correcting the nominal phase law and representative of variations in the relative positions of the sources. This system has application to geological prospecting by seismic surveying at sea.

Abstract: A monoport airgun for seismic exploration has a single discharge port extending continuously for 360.degree. around its longitudinal axis. This airgun has a first housing providing a firing chamber containing pressurized gaseous fluid (gas) and a second housing providing an operating chamber. The first and second housings are positioned in alignment along the longitudinal axis. They are spaced apart along this axis for defining the discharge port between them extending continuously around the axis. The two housings of the monoport airgun are interconnected solely by a guide member concentric with the axis. A shuttle encircling the guide member is movable therealong between closed and open positions. In closed position, the shuttle closes the firing chamber for retaining pressurized gas therein. In open position, the shuttle opens the firing chamber to the discharge port for allowing pressurized gas to blast from the firing chamber through the discharge port.

Abstract: A seismic energy source for producing pressure pulses is disclosed. The source contains a substantially symmetrical main chamber for storing compressed fluid. Two shuttles adapted to abut against each other are slideably placed around the housing to sealingly enclose the chamber. A separate control chamber for each shuttle is formed to urge its associated shuttle against the other shuttle when pressurized fluid is supplied to the control chamber. A separate firing chamber is formed for each shuttle between the shuttle and the housing. The firing chambers are activated by the fluid from the main chamber to simultaneously move both the shuttles away from each other to allow the compressed fluid to discharge from the main chamber into the surrounding medium.

Abstract: A shuttle air gun for generating an acoustic output for seismic testing having improved wear rings and seals is provided. The composition of the wear rings includes polytetrafluoroethylene. The composition of the seals includes polyester and Teflon oil. A vent assembly overlying a firing chamber vent check valve eclipsing an firing chamber vent is also provided. The vent assembly limits the movement of an O-ring check valve when compress air is vented from the firing chamber.

Abstract: A control valve for use in geophysical surveying is disclosed. The valve contains a housing having a through bore intersecting with a fluid path. The fluid passes from an input port to an output port. A seat having recess thereof is placed in the fluid path in the through bore. A poppet assembly is attached to the through bore at the end opposite to the seat. The poppet assembly contains a poppet one end of which is adapted to match the recess and moveable in opposite directions by a motor. A decoder is coupled to the motor for causing the motor to turn in the desired direction. When the motor is turned in one direction, the poppet moves toward the seat and completely closes off the fluid path between the input and output ports. To open the valve, the motor is moved in the opposite directions to move the poppet away from the seat until the fluid path is open.

Abstract: The invention provides a floatation apparatus for maintaining a longitudinal object at a constant depth below the water surface in a body of water. Several airtight chambers are connected in a serial connection to form a string of air tight chambers. A one-way check valve is installed in the chamber at one end of the string while the other end chamber is connected to a nose piece. Air is continuously supplied to the check valve connected to the end chamber. A separate one-way check valve is installed between each pair of adjacent chambers in the string in a manner that air can pass between only in the direction from the air source to the nose member. The floatation apparatus is pivotaly connected to the longitudinal object at more than one place by means of parallel links.

Abstract: In seismic surveys at sea, with seismic devices, especially sources of seismic energy being towed behind a vessel and kept at a mutual configuration relative to each other, and with the devices being suspended from a buoyancy member (1) mechanical structure of the equipment permits undesirable forces which influence the sources of seismic energy (3), especially during firing, to be absorbed. Mutually arranged flexible, resilient members (4) are provided between the suspension line of the seismic devices (3) and the seismic devices (3) and/or between the seismic devices. Seismic devices are supported on two or more rigid fastening members (5) and flexible resilient members (4) extend between the fastening members and the suspension line. The flexible resilient members (4) preferably extend in a curved path between the fastening members (5) and the members together form an integrated unit.

Abstract: In towing sources of seismic energy behind a vessel, especially in connection with seismic surveys in waters which are covered with ice, the buoyancy floats and also the sources of seismic energy are readily influenced by broken up ice collecting behind the icebreaking towing vessel. In order to stabilize the tow of sources of seismic energy a towing line (7) is secured between the buoyancy means (4) belonging to the tow of sources of energy (3) and the vessel (1) at a point (10) which is located in the area of the waterline, so that towing line (7) will extend in the area of the waterline. Another towing line (8) is connected directly with the array of sources of seismic energy (5) and is secured to a towing point (11) on the vessel (1) located below the waterline. An arrangement is also disclosed for securing the towing line (8) in a suitable location to avoid influence from ice and, furthermore, the design of floats (4) avoids influence from the ice.

Abstract: A compact, marine acoustical source is disclosed. More specifically, the present invention relates to a marine acoustical source capable of producing a strong primary pulse while substantially suppressing or eliminating undesired secondary pulses derivative from said primary pulse.

Abstract: The invention provides a seismic transmitter source system which includes a floatation device that contains a plurality of air tight chambers in a serial connection. A separate one way check valve is placed between each adjacent pair of the chambers. Pressurized air is continuously supplied to an end chamber. The one-way check valves enable the air to pass to the remaining chambers in one direction. A transmitter subarray containing a plurality of spaced apart transmitters is suspended from the floatation device by means of severasl pivotly connected links. The front end of the transmitter array is connected to a point near the front end of the floatation device. During operation, the seismic transmitter source system is pulled from a tow point located at the front of the floatation device, pulling both the floatation device and the transmitter subarray in substantially a horizontal straight line position while maintaining the transmitter subarray at a near constant depth below the water surface.

Abstract: A sleeve for a seismic air gun exhaust chamber is disclosed. The sleeve prevents water from accumulating in the air gun exhaust chamber when the air gun is vertically positioned and provides a convenient method for regulating the volume of the air gun exhaust chamber, and thus the frequency of acoustic energy emitted by the gun. The sleeve is characterized by a false bottom which is connected to the main chamber by an orifice and passages.

Abstract: A compact, marine acoustical source is disclosed. More specifically, the present invention relates to a marine acoustical source capable of producing a strong primary pulse while substantially suppressing or eliminating undesired secondary pulses derivative from said primary pulse.