GB131038A - Improved Means for Detecting and Locating Subaqueous Sounds. - Google Patents

Abstract

131,038. Sykes, A. F. March 28, 1918. Locating subaqueous sounds.- To eliminate " water-noise " or like disturbance in apparatus for detecting and locating subaqueous sounds, the detecting-instrument, which is described in Specification 15320/15, preferably a hydrophone of the type is enclosed within a shield of such thickness and strength as to vibrate as a whole, so that disturbances are eliminated by an averaging process. A suitable material for the shield is wood impregnated with paraffin wax. Externally, the shield may be of torpedo or other form suitable for towing, or may be spherical, or may take the form of a fishing float. When towed, the apparatus is maintained at suitable depth by a float, which may be interposed between the shield and towing-vessel, or may be trailed by the shield. The interior of the shield is filled with liquid in which the hydrophone is placed. Means are provided to allow expansion and contraction of the enclosed liquid. Specification 15024/14 also is referred to. Fig. VI shows a sphenical shield in two parts 1, 2 having metal parts 14, 15 which screw together. A bifilar suspension 8 is provided. The hydrophone is supported bv rubber butters 5 which may be expanded on the pickle-bottle stopper principle to engage recesses 18 in the hydrophone ring. The leads 20 pass through a member 21 between which and the wall of the sphere is an annular recess putting the liquid-filled space 6 in communication with the external water to allow expansion &c. of the contained liquid without injury to the shield. Or a small opening may be drilled through the wall of the shield for the same purpose. In a modification, the leads are combined with the supports 8, and in one form pass out through two of the buffer supports 5. In another modification, the hydrophone is mounted on a vertical diaphragm 12, Fig. III., which divides the shield into two chambers, each having a vent-hole 9. The supports 8 are provided with streamline masses 13 to minimize vibration. In a further modification, the diameter of the hydrophone ring 4 is practically equal to that of the spherical shield, the two parts of which are mounted close to the opposite faces of the ring and separated therefrom by rubber buffers. In one form on these lines, the shield members 1, 2. Fig. VIII., are secured by screws 28 surrounded by rubber 5 and passing through the ring 1, flanged rings 24 carried by the parts 4, 2 being positioned a short distance from the ring 4 as shown. Other modifications show the shield in the form of a cup or cylinder enclosing the hydrophone which is mounted depending from a massive support. When intended for towing, the shield preferably has a streamline form, as shown in Fig. I., and the chamber 6 is preferably hermetically sealed. To allow for expansion &c. of the contained liquid, a yielding device is employed, such as a rubber tube 52 extending across the chamber 6 and communicating at its ends with the external water. In a modification in which the hydrophone is mounted to receive transverse vibrations, the ring has a wedge-form cross-section, the thicker and heavier side. keeping lowermost. In a further form, the chamber 6 has a cylindrical lining jacket, the contained liquid being in contact with the members 1, 2 only at the ends of the cylinder. An annular air space exists between the cylinder wall and the shield, and the rubber tube extends through the air space in the hydrophone and communicates at its ends with the liquid in the chamber. In a further modification applicable to non-directional detectors as applied to the hulls of ships, the microphone is carried by a diaphragm at the bottom of a recess, the mouth of which is substantially closed by the shield member. Fig. XI. shows a .similar type of screen applied to a directional hydrophone heavily recessed in its ring 4, the shields 1 (in this case in duplicate) being mounted to close the mouths of the recesses. In each case, the recesses constitute the liquid-filled chamber. Rubber or other sound-insulating material is interposed between the supports or towing-cable and the shield. Several such arrangements are described.