# US 2016/0259074 A1 · Air-Spring Compensation in a Piston-Type Marine Vibrator > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2016/0259074 A1 - Document ID: US20160259074A1 - Status: Published application - Kind: A1 - Application number: 15/153,467 - Filed: 2016-05-12 - Published: 2016-09-08 - Earliest claimed: 2013-09-20 - Assignees: PGS Geophysical AS - Applicants: PGS Geophysical AS - Inventors: Stig Rune Lennart Tenghamn; Jonathan David Snodgrass; Bo Carl Fredrik Lövgren; Karl-Henrik Ryttersson - Web page: https://patentgrep.com/patent/US20160259074A1 ## CPC - G01V 1/04: Details - G01V 1/143: using mechanical driving means {, e.g. motor driven shaft}(G01V1/104, G01V1/133 take precedence) - G01V 1/145: by deforming or displacing surfaces {, e.g. by mechanically driven vibroseis™} - G01V 1/159: {using piezoelectric or magnetostrictive driving means (generating mechanical vibrations by using piezoelectric or magnetostrictive effect in general, B06B1/06, B06B1/08)} - G01V 1/38: specially adapted for water-covered areas (G01V1/28 takes precedence) - G01V 2210/1293: Sea - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract Embodiments relate to the restriction of gas flow in a piston-type marine vibrator to compensate for air-spring effects. An embodiment provides marine vibrator comprising: a containment housing; a piston plate; a fixture coupled to the containment housing; a mechanical spring element coupled to the piston plate and to the fixture; a driver coupled to the piston plate and to the fixture; and a variable gas flow restrictor disposed in an interior volume of the marine vibrator, wherein the marine vibrator has a resonance frequency selectable based at least in part on the variable gas flow restrictor. ## Claims ### Claim 1 A marine vibrator comprising: a containment housing; a piston plate configured to act on water surrounding the marine vibrator to produce acoustic energy; a fixture coupled to the containment housing; an interior volume at least partially defined by the containment housing and the piston plate; a mechanical spring element coupled to the piston plate and the fixture; a driver coupled to the piston plate and the fixture; and a variable gas flow restrictor disposed in the interior volume of the marine vibrator and movable to seal off a portion of interior volume. ### Claim 2 (depends on 1) The marine vibrator of claim 1, wherein the variable gas flow restrictor comprises pneumatically or hydraulically adjustable openings. ### Claim 3 (depends on 2) The marine vibrator of claim 2, wherein the pneumatically or hydraulically adjustable openings are fitted with louvers. ### Claim 4 (depends on 1) The marine vibrator of claim 1, wherein the marine vibrator has at least one resonance frequency of about 10 Hz or lower when submerged in water at a depth of from about 0 meters to about 300 meters. ### Claim 5 (depends on 1) The marine vibrator of claim 1, wherein the driver is a moving coil driver or a linear servo motor. ### Claim 6 (depends on 1) The marine vibrator of claim 1, comprising another variable gas flow restrictor disposed in the interior volume of the marine vibrator. ### Claim 7 (depends on 1) The marine vibrator of claim 1, wherein the gas flow restrictor comprises a sliding-plate structure. ### Claim 8 (depends on 1) The marine vibrator of claim 1, wherein the variable gas flow restrictor is remotely controlled. ### Claim 9 (depends on 1) The marine vibrator of claim 1, wherein the mechanical spring element comprises at least one type of spring selected from the group consisting of: a bow spring, a coil spring, a flat spring, and a leaf spring. ### Claim 10 (depends on 1) The marine vibrator of claim 1, wherein the piston plate is coupled to the containment housing by way of a rubber seal, the piston plate covering an opening in a first surface of the containment housing. ### Claim 11 (depends on 1) The marine vibrator of claim 1, wherein the marine vibrator further comprises a mass spring element having weights affixed thereto, the mass spring element being coupled between the fixture and the piston plate. ### Claim 12 A method comprising: towing a marine vibrator in a body of water in conjunction with a marine seismic survey, wherein the marine vibrator comprises adjustable openings movable to seal off a portion of an internal volume of the marine vibrator; triggering the marine vibrator to cause one or more piston plates in the marine vibrator to move back and forth wherein one or more mechanical spring elements exert a biasing force against the one or more piston plates; and adjusting the adjustable openings based on depth of the marine vibrator in the body of water to vary the gas flow in an internal volume of the marine vibrator. ### Claim 13 (depends on 12) The method of claim 12, wherein the marine vibrator is towed at a first depth of from about 0 meters to about 300 meters, wherein the method further comprises towing the acoustic vibrator at a second depth, and wherein the gas flow is restricted in the marine vibrator when towed at the first depth such that a first resonance frequency of the acoustic vibrator is substantially constant when towing depth varies from the first depth to the second depth. ### Claim 14 (depends on 12) The method of claim 12, wherein the adjustable openings are fitted with flappers or a guillotine device. ### Claim 15 (depends on 12) The method of claim 12, wherein the adjusting the adjusting openings adjusts an air spring stiffness. ### Claim 16 (depends on 12) The method of claim 12, wherein the adjusting comprises adjusting a diameter and spacing of the adjustable openings. ### Claim 17 (depends on 12) The method of claim 12, wherein the marine vibrator generates a first resonance frequency within a frequency range of about 1 Hz and about 10 Hz. ### Claim 18 (depends on 12) The method of claim 12, wherein the adjustable openings are pneumatically or hydraulically adjustable. ### Claim 19 (depends on 12) The method of claim 12, further comprising: obtaining geophysical data; and processing the geophysical data to generate a geophysical data product, wherein the geophysical data product is obtained by a process that includes detecting acoustic energy originating from the marine vibrator. ### Claim 20 (depends on 19) The method of claim 19, further comprising recording the geophysical data product on a tangible, non-volatile computer-readable medium suitable for importing onshore.