Abstract: A Vibration Isolation Module (VIM) for a towed acoustic streamer includes cylindrical masses attached at regular spacing to a central core of viscoelastic damping material, which may be extruded over a snubbed elastic strength member. Further snubbed elastic strength members may be attached around the outer diameter of the masses. Viscous "dash-pot" type dampers are installed within the masses. The space between the masses is filled with open cell plastic foam, around which is wrapped a layer of power and data cables. A jacket of damped thermoplastic is extruded over the cable layer and caps containing a fluid filling valve are attached at each end of the module, and the interior void is filled with a low density, high viscosity fluid. The "dash-pot" type dampers can be replaced by a stocking which, under extension, compresses the foam and forces fluid through pores of the foam, thus simulating the viscous damping of the "dash-pot" type dampers.

Abstract: A tow cable includes a high density, high damping core of a material such as lead, surrounded by a layer of helically wrapped or braided strength fibers of a material such as steel, or alternatively, of aramid fibers. Over this is provided a layer of a resilient, deformable thermoplastic material such as polyurethane, to provide for movement of the subsequent data-bearer layer under strain, so that no strain is applied to the data-bearer themselves. Around this layer is provided a layer of helically wrapped (or braided) power and data bearers, the bearers including coaxial cables, twisted pairs, and fiber optic bearers. To ensure water-blocking, this layer may be enclosed in an extrusion of thermoplastic material, such as polyurethane. Around this is wrapped or braided a layer of protective fiber, of material such as steel or aramid fiber, and over this, in a roughly trochoidal cross-section, is extruded an outer layer of thermoplastic material, such as polyurethane.

Abstract: A jacket for a liquid filled towed array is formed from a composite material formed from short lengths (typically 2-4 mm) of reinforcing fibre (1) which are mixed with a thermoplastic material (2) to form the jacket (3). The reinforcing fibre (1) is preferably either glass fibre, aramid fibre, or carbon fibre or a mixture thereof and provides the desired high Tensile Modulus. The thermoplastic material (2) provides a relatively high level of viscoelastic damping (that is a high, or at least medium, Loss Tangent). The fibres (1) and thermoplastic material (2) are mixed, or compounded, by the material supplier and the material for the jacket (3) provided in granular form to the extrusion contractor. The manufacture of the jacket (3) is undertaken by normal extrusion processing.

Abstract: An acoustic sensor module, contains groups of single sensor elements within a fluid-tight enclosure. The enclosure is bounded by a reinforced hose wall and module end caps at either end of the module. The sensors are mounted in the center of the enclosure using tubular foam spacers; smaller cylindrical foam spacers fill the central space between sensors. Radial stiffness is provided to the spacers by thin annular rings held in place by fine strength cords. Thin flexible wires connect the sensor elements of each group to the preamplifying/multiplexing electronic package, the connecting leads therefrom being brought out to the outer surface through a division between spacers. Data and power cables are spirally wrapped around the outer diameter, with an over-wrap of fine fiber or plastic tape to lock them into position. The connecting leads to the electronic packages are then spliced into their respective data/power cables.

Abstract: A hydrophone cable having a series of hydrophones (7) at spaced intervals along the cable and having strength members (1) and transmission line conductors (3) extending along the cable in which a braided construction (2, 3, 4 and 5) is used which can be loosened to insert the hydrophones (7) into cable, voids in the cable being filled with a buoyant gel and the assembly covered by an outer plastic sheet (6).