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: A solid marine seismic cable assembly includes communication coil housings which clamp around a cable in a spaced-apart relationship. The cable has a central axis. Each housing contains at least two communication coils adapted for communicating with an adjacent external device. Two of the communication coils, whether or not adjacent to one another, are offset at least 90.degree. from each other about the axis of the cable. The external devices affix to the cable assembly in a spaced-apart relationship corresponding to the spaced-apart relationship of the communication coil housings. Each external device has a unit which communicates with the communication coil via magnetic induction signals.

Abstract: A solid marine seismic cable assembly includes a cable, hydrophone housings, a buoyant filler, and an outer protective jacket. The cable includes a load-bearing fiber bundle, data-transmitting wires, power conductors, optical fibers, and a protective sheath. The data-transmitting wires, power conductors, and optical fibers surround the load-bearing fiber bundle. The protective sheath surrounds the assembly of the data-transmitting wires, power conductors, optical fibers, and the load-bearing fiber bundle. The hydrophone housings affix around the cable in a spaced-apart relationship. Each hydrophone housing includes a hydrophone module, and each hydrophone module contains a hydrophone. The buoyant filler surrounds the cable, and separates the hydrophone housings. The outer protective jacket surrounds the hydrophone housings and the buoyant filler, enclosing the cable assembly.

Abstract: A low-profile hydrophone module for a marine seismic system includes a block having a curved surface and a receiving surface in which an open cavity is disposed, a hydrophone assembly, to which lead wires attach, disposed in the cavity, lead wires which pass out of the cavity, and a sound-transmitting material which fills the cavity. In another feature, the hydrophone assembly includes a hydrophone and a baffle material, the baffle material enclosing the hydrophone, the cavity is sealed around the lead wires, the sound-transmitting material is oil, and a cover sealingly affixes over the cavity. In another feature, the hydrophone assembly includes a hydrophone and a frame, the cavity is sealed around the lead wires, the sound-transmitting material is a potting sealant, and a cover sealingly affixes over the cavity.

Abstract: A hydrophone housing includes a hydrophone module, or cap, which contains a hydrophone. The hydrophone housing clamps around a marine seismic cable. The hydrophone housing farther includes a first portion and a second portion. One of the portions has a receiving recess, The hydrophone cap installs on this receiving recess. The portions each include a contact surface which contacts the cable when the portions fasten around the cable. The portions clamp around the cable via screws, The contact surface includes raised bosses which securely grip the cable by increasing contact pressure per unit area in a region of contact between the raised bosses and the cable.In another feature, the portion which contains a receiving recess further includes a wire-clearance recess and a wire passageway, between the receiving recess and the wire-clearance recess.In another feature, an outer cylindrical surface of each hydrophone cap is flush with an outer cylindrical surface of each hydrophone housing.

Abstract: An acoustic transducer assembly includes a piezoelectric ceramic crystal. The assembly also includes a pair of solid circular metal plates positioned to sandwich the piezoelectric ceramic crystal between them, wherein each of the metal plates comprises: (i) an outer rim circling a concave portion formed in a first surface of the metal plate, the first surface oriented toward the piezoelectric ceramic crystal; and (ii) an epoxy wicking barrier formed in the first surface, adjacent to the outer rim. The assembly also includes an epoxy adhesive interposed between the metal plates and the piezoelectric ceramic crystal, wherein the outer rim of each plate is bonded to the piezoelectric ceramic crystal by the epoxy adhesive, the pair of plates thus forming a cavity between them. The assembly also includes a flexing stop attached to each first surface.

Abstract: A hydrophone-filter with the frequency response characteristics of a geophone utilizes a second order high pass filter wherein one capacitive element of the filter is the hydrophone itself. The filter includes an amplifier, wherein one input receives a biasing voltage from a resistive network, and the other input receives a signal provided by one or more hydrophones. The filter also includes one or more capacitive elements and one or more resistive elements. The natural frequency and slope of the filter depend upon the values of the capacitive elements of the circuit, including the capacitance of the hydrophones, as well as the values of the resistive elements of the circuit. Advantageously, the natural frequency of the hydrophone-filter remains constant even if the magnitude of the hydrophone's output changes.

Abstract: A method for precisely adjusting the sensitivity of a polarized crystal hydrophone by applying a voltage signal to the hydrophone. Voltage pulses having selected characteristics are repeatedly applied to the crystal until it is determined that the sensitivity of the crystal has reached a desired level.

Abstract: An improved seismic array is disclosed having a plurality of seismic detector connection points with a seismic detector at each seismic detector connection point. The output of each seismic detector in the array is weighted by providing first resistive weighting at each seismic detector connection point. The weighted output of all detectors in the array is provided to a first end of the array over a single pair of wires. An amplifier is additionally provided for connection to the pair of wires at the first end of the array, and the amplifier has feedback network, including a resistor. The ratio of the value of the resistance in the feedback network to the value of the weighting resistor at a seismic detector connection point determines the magnitude of the signal appearing at the output of the amplifier from the response from the seismic detector at that point.

Abstract: An improved seismic array and method of seismic exploration are provided which have the capability to supply data to separate recording stations simultaneously. The seismic array has a plurality of seismic detector connection points, and a seismic detector is located at each seismic detector connection point. The outputs of the seismic detectors are electrically isolated from each other, and weighting may be applied to the output of each seismic detector in the array. Two signal-carrying media are also provided in the array, and the weighted outputs of the seismic detectors are conveyed to the first end of the array over one signal-carrying medium and to the second end of the array over the second signal-carrying medium. A Chebychev weighted array is achieved by a proper selection of weighting.

Abstract: An improved seismic array is provided which has the capability to supply data to adjacent recording stations simultaneously. The seismic array has a plurality of seismic detector connection points, and a seismic detector is located at each seismic detector connection point. Dual weighting of the output of each seismic detector in thearray is achieved by connecting dual resistors to the output of each seismic detector. Two pairs of wires are also provided in the array, and one pair of wires interconnects one weighted output of each seismic detector to the first end of the array. The second pair of wires interconnects the second weighted output to the second end of the array. An amplifier is provided for use at either or both ends of the array, and a feedback network, including a resistor, is associated with the amplifier.