Abstract:
In a seismic streamer cable, stress sensors are co-located with the hydrophones in the cable. The stress sensors are responsive to mechanical stresses applied to the cable but it are substantially unresponsive to acoustic waves propagating in fluid media. The signal outputs from the stress sensors are combined with the signal outputs from the corresponding co-located hydrophones to cancel spurious signals due to bulge waves.
Abstract:
For a simplified towed array configuration an integrated hydrophone, preamplifier and telemetry hybrid unit suitable for connecting with a single coaxial cable was developed. The preamplifier and FM hydrophone telemetry assembly comprises an air backed ceramic assembly connected to a preamplifier/voltage control oscillator chip. In addition the chip includes a regulator and power separation network.
Abstract:
A hosewall terminating apparatus for a streamer section utilizing a load bearing flexible hosewall includes an inner sleeve having radially extending outward protrusions and an outer sleeve having radially extending inward protrusions. With the inner sleeve positioned within the outer sleeve, the radial distance between ends of these protrusions are spaced-apart to provide a gap for the position of the flexible hosewall of the streamer section. The hosewall of the streamer section is secured between these protrusions and the sleeve surfaces when the outer sleeve is reduced in diameter by swaging.
Abstract:
An angular member provided on seismic cables towed by a vessel and laterally displaced in parallel and in relation to the course of the vessel comprises a frame at least partly enclosing the cable in the area of angular deflection between an inner cable portion extending obliquely to the towing direction and the active main cable portion. The frame is formed of two frame plates secured in spaced relationship and having at the lead-in end for the cable a cable-fastening device and at the other end a pivotable ramp swingable in the plane of the frame plates. The ramp has a further fastening device for the cable. Another fastening device is pivotably connected to the frame plates for connecting thereto a wire to a paravane or the like. When towed in the water the angular member absorbs most of the forces normally exerted on the cable at the area of angular deflection.
Abstract:
A flexible line array transducer assembly for detecting underwater acoustical signals. The assembly includes an array of spaced-apart piezoelectric elements arranged generally in a line and selected to have low cross-coupling characteristics, low sensitivity to incoherent mechanical perturbations in the directions longitudinal and lateral to the axis of the array, and high sensitivity to coherent mechanical perturbations such as acoustical signals. The elements are polarized in a direction generally transverse to the array and each include opposing surface areas which are generally parallel with the linear axis of the array. Electrodes are disposed on the opposing surface areas of the elements and are coupled to conductors which carry signals produced by the piezoelectric elements when the elements are stressed by acoustical signals. A porous, open-cell material is disposed about the piezoelectric elements as an encasement to maintain the elements in place and mechanically isolate the elements. An outer, water-tight jacket encloses the open cell material and holds a fill fluid carried within the open-cell material. An electrically conductive flexible sleeve may be placed either about the open-cell material or about the outer jacket to shield the piezoelectric elements from electromagnetic waves.
Abstract:
An acoustic transducer is provided that uses a layer of magnetostrictive ferromagnetic material having high magneto-mechanical coupling. The ferromagnetic material is adhered to a part of the outer surface of a resilient rod, so that an incident acoustic signal causes a change in stress in the magnetic material and, in turn, a change in the material's magnetization. An electrical coil surrounds the magnetic material and converts the changing magnetization into an electrical signal. A plurality of transducers may be assembled into an array and towed behind a ship to detect underwater acoustic signals.
Abstract:
A marine seismic cable comprising a core; a housing coupled to the core and having a cavity adapted for holding a hydrophone, the cavity being located on a first side of the housing; elastic material positioned in the cavity and extending beyond the boundary of the cavity, a hydrophone positioned in the elastic material in the cavity; and a rigid plate positioned adjacent to the elastic material.
Abstract:
A hydrophone section for a seismic streamer towed array in which the hydrophones 2 are arranged in groups of not more than 7, the spacing of the hydrophones within each group being such that each group has an overall length l=0.8-1.2 m. The hydrophone mounts 5 and mechanical spacers 3 are attached at their periphery to aramid fibre strainwires 4. The hydrophone mounts and mechanical spacers are acoustically open structures.
Abstract:
The invention relates to novel laminate tubular articles comprising an outer layer having a modulus of at least about 10.sup.7 Pascals, an interior layer comprising a polymeric material having a loss tangent of at least about 0.5 at a temperature of from about 0.degree. C. to about 40.degree. C. at a frequency of from 10-4,000 Hz and whose modulus is less than the modulus of the outer layer and an innermost layer having a modulus greater than the modulus of said interior layer. The invention further relates to a device for sensing in a body of water, said device comprising at least one sensor surrounded by the novel laminate tubular articles of the invention. The mechanical and acoustic properties of the article make it particularly appropriate for use as the hose in a towed-array sonar system.
Abstract:
A vibration isolation module (30) includes termination members (34, 36) at each end to which are connected electrical wires or cable (39), and a braided rope of aramid fiber (32). A plurality of compliant members (40) of polyurethane hose having tapered ends are inserted at intervals within the braided strands of the rope (32). Some of the compliant members (40) may be filled solid with polyurethane. Variable lengths of hose or variable diameters and wall thicknesses may be used to vary the compliance of the compliant members (40). Between the compliant members (40) are positioned a number of spacer members (38) which provide support for the hose (37) and electrical wires (39). This structure is carried within an oil filled stretchable hose (37) fastened to the termination members. When the module (30) is subjected to forces in tension, the load is carried by the aramid fiber rope (32) which, as the load is increased, tends to squeeze down and compress the compliant members (40).