Earth vibrators, such as servo-hydraulic vibrators, are improved to produce more output force and less distortion at very low frequencies by capturing mass from the vehicles which carry them, adding sufficient inertial mass to the reaction mass without adding much vehicle and equipment weight while also avoiding increases to the servo-hydraulic vibrator's stroke length. In particular, improvements to servo-hydraulic vibrators, at low frequencies, will couple some mass from the carrier vehicle frame and its load using non-rigid coupling only when additional mass is needed using dampers connected between the reaction mass and the carrier vehicle's frame, with the added damping being applied by a control system at very low frequencies of output where the vibrator is otherwise unable to produce force equal to its hold-weight.

Earth vibrators, such as servo-hydraulic vibrators, are improved to produce more output force and less distortion at very low frequencies by capturing mass from the vehicles which carry them, adding sufficient inertial mass to the reaction mass without adding much vehicle and equipment weight while also avoiding increases to the servo-hydraulic vibrator's stroke length. In particular, improvements to servo-hydraulic vibrators, at low frequencies, will couple some mass from the carrier vehicle frame and its load using non-rigid coupling only when additional mass is needed using dampers connected between the reaction mass and the carrier vehicle's frame, with the added damping being applied by a control system at very low frequencies of output where the vibrator is otherwise unable to produce force equal to its hold-weight.

A submersible sound system may include a housing, an end piece, an elastic membrane, an end cap affixed to the elastic membrane, and a subwoofer speaker system disposed within the housing and supported by a speaker support. A bubble sound source may be defined by the speaker support, the speaker diaphragm, an anterior end of the housing, the elastic membrane, and the end cap. The housing, end piece, and a posterior surface of the speaker support may form a sealed enclosure. The sound system may include a tuning pipe disposed between the sealed enclosure and the bubble sound source. A Helmholtz resonator may be disposed anteriorly of the speaker system. Multiple sound system may be assembled to form a cluster. The cluster may be defined by the vertices of regular polyhedron. The sound systems may be controlled to maintain the speaker systems within acceptable thermal limits.

A seismic marine vibrator (100) may comprises first plates (102) and second plates (104) arranged along a longitudinal axis (101), longitudinal and peripheral first (106) and second (108) elements respectively secured to the first (102) and second (104) plates, and an actuator (112) operable to reciprocate the first elements (106) relative to the second elements (108) along the longitudinal axis (101) so as to reciprocate the first plates (102) relative to the second plates (104). The seismic marine vibrator further comprises peripherally closed air-filled chambers (109) and peripherally open chambers (111), the volume of said open chambers (111) being varied when the first plates (102) are reciprocated so as to take in and expel water radially to generate an acoustic wave. This forms an improved seismic marine vibrator.

An improved servovalve for a seismic vibrator or vibration machine which includes a left additional passageway conducting a portion of sampled pressure from a left cylinder pressure chamber to only a portion of the right end drive surface of the spool, wherein the portion of the right end drive surface is less that of the entirety of the right end drive surface; and a right additional passageway conducting a portion of sampled pressure from a right cylinder pressure chamber to only a portion of the left end drive surface of the spool, wherein the portion of the left end drive surface is less that the entirety of the left end drive surface; thereby providing at least two additional passageways configured to provide linear proportional pressure feedback in spool movement control.

A submersible sound system may include a housing, an end piece, an elastic membrane, an end cap affixed to the elastic membrane, and a subwoofer speaker system disposed within the housing and supported by a speaker support. A bubble sound source may be defined by the speaker support, the speaker diaphragm, an anterior end of the housing, the elastic membrane, and the end cap. The housing, end piece, and a posterior surface of the speaker support may form a sealed enclosure. The sound system may include a tuning pipe disposed between the sealed enclosure and the bubble sound source. A Helmholtz resonator may be disposed anteriorly of the speaker system. Multiple sound system may be assembled to form a cluster. The cluster may be defined by the vertices of regular polyhedron. The sound systems may be controlled to maintain the speaker systems within acceptable thermal limits.

The disclosure herein generally relates to a device for use in marine seismic surveying. A displacement apparatus has a base and an actuated head. The actuated head is coupled to an actuation means comprising a shaft, a cam, and a motor. The cam is coupled to the shaft at a radial position from the center of the cam. A vacuum piston is optionally coupled to the actuation means. A variable resonance spring, such as an air spring, is coupled to the actuated head in order to tune the apparatus to operate in resonance at a range of frequencies.

The disclosure herein generally relates to a device for use in marine seismic surveying. A displacement apparatus has a base and an actuated head. The actuated head is coupled to an actuation means comprising a shaft, a cam, and a motor. The cam is coupled to the shaft at a radial position from the center of the cam. A vacuum piston is optionally coupled to the actuation means. A variable resonance spring, such as an air spring, is coupled to the actuated head in order to tune the apparatus to operate in resonance at a range of frequencies.

A compact seismic source for seismic acquisition generating a humming signal includes a casing and a low-frequency reciprocating drive. The casing defines a fluid tight chamber and comprises a first casing section and a second casing section of roughly equal mass. The drive is disposed within the fluid tight chamber and, in operation, reinforces the natural reciprocating oscillation of the first and second casing sections relative to one another at a low seismic frequency. In one aspect, this action omni-directionally radiates the low frequency, humming seismic signal. On another aspect, the compact seismic source is substantially smaller than the wavelength of the low seismic frequency. Such a compact source may be deployed to omni-directionally radiate a low frequency, humming seismic signal during a seismic survey.

A compact seismic source for seismic acquisition generating a humming signal includes a casing and a low-frequency reciprocating drive. The casing defines a fluid tight chamber and comprises a first casing section and a second casing section of roughly equal mass. The drive is disposed within the fluid tight chamber and, in operation, reinforces the natural reciprocating oscillation of the first and second casing sections relative to one another at a low seismic frequency. In one aspect, this action omni-directionally radiates the low frequency, humming seismic signal. On another aspect, the compact seismic source is substantially smaller than the wavelength of the low seismic frequency. Such a compact source may be deployed to omni-directionally radiate a low frequency, humming seismic signal during a seismic survey.