Patent ID: 8687464

Claim:
A marine seismic source suitable for producing seismic signals over a band of frequencies comprising: a reservoir for containing water; a flow path between the reservoir and a body of water; means to cause water in the reservoir to flow into the body of water via the flow path; means to modulate an area of the flow path whereby the flow of water from the reservoir into the body of water is modulated to produce a modulated pressure signal in the body of water; and a buffer means configured to minimize fluctuations in static pressure of the water within at least one of the reservoir and flow path as the area of the flow path is modulated, the buffer means comprising a plenum for containing gas in communication with at least one of the reservoir and flow path and arranged such that water from the reservoir or flow path can flow into or out of the plenum in contact with the gas as the area of the flow path is modulated, wherein the means to modulate comprises a stator and a rotor mounted coaxially with the stator, the stator and rotor being located within the flow path, the stator and rotor each having at least one aperture wherein the apertures overlap as the rotor rotates, the overlap of the apertures falls to zero at one or more angular positions of the rotor, the apertures of the stator and rotor are shaped so that the area of overlap of the apertures in the rotor and stator varies smoothly as the rotor rotates, and that the rotor and stator are mounted sufficiently close to one another that when there is no overlap of the apertures the flow of water into the body of water is substantially smaller that when the apertures overlap fully.