Patent GB-191515320-A (GB)
Title: Improved Means for Detecting and Locating Subaqueous Sounds.
Inventor: SYKES ADRIAN FRANCIS
IPC: G01S1/72
Filed: 1915-10-30
Abstract: 15,320. Sykes, A. F., and Morris, J. T. Oct. 30. [Cognate Applications, 5084/16 and 6700/16.] Locating sounds; subaqueous sound signals.- A device for detecting and locating subaqueous sounds comprises an immersed body having two opposite sides exposed to the water so that it vibrates under differences betw'een simultaneous pressures on opposite sides due to passage of a sound wave, as distinguished from variations of pressure at any one point. The vibrations may be detected by any suitable means, such as a microphone. The mechanical connexions with the microphone are such that vibration takes place most readily in a priedetermined direction, so that when this direction coincides with the direction of the sound wave, the detected sound is a maximum. The immersed body is of specifically light material or is hollow, to give low apparent density. As shown in Fig. 1, the immersed body is a disk 1 on an arm 2 passing through a flexible sleeve to the interior of a casing 4 containing a relatively heavy mass 6 acoustically insulated from the casing by rubber 7. The arm 2 carries the microphone 8 and is connected to the mass 6 by a spring strip 5 capable of torsional vibration. This device is most responsive when a face of the disk is towards, and least responsive when the disk is edge-on to, the source of sound. In a modification, the disk is omitted and the casing serves as the vibrating body. In further modifications in which the vibrating body is hollow, opposite faces of the body are connected by an internal strut or tie-bar, and vibrations are communicated to the arm carrying the microphone through a wire or link connexion which only transmits longitudinal vibrations. In this form, the microphone is most responsive when the wire is parallel to the direction of sound propagation. In one such modication, Fig. 9, the immersed body 21 is a sphere with a diametral plate 22 and is carried by a flexible stalk 23 connected to a base (not shown) resting on the sea-bottom and containing a motor by which the stalk can be rotated the desired amount from a distance. The arm 2 carrying the microphone 8 is pivoted to an acoustically insulated mass 6 and receives vibrations through a wire 20. The back of the microphone 8 may be carried by a counterbalanced arm 25, Fig. 11, torsionally pivoted to the arm 2. To increase the efficiency of the device, the immersed body mav be mounted in a hole in a massive slab of dense material 28, Fig. 14. In this case, the face-plates 15 of the immersed body are connected by a strut 19, on which the microphone is directly mounted. In a modification, the immersed body comprises two plates connected by a tubular strut with coned ends and supported by rubber rings let into grooves in the hole. In a further modification, the plates 15 are integral with the slab 28. The vibrations may be mechanically amplified by the method of mounting the microphone shown in Fig. 18. The arm 2 carrying the microphone 8 is mounted on a diaphragm 31 carried by the strut 19, and a comparatively heavy ring 33 is carried by a diaphragm 32 connected to the arm. A plurality of immersed bodies may be mounted in holes in the same slab of dense material, with the microphones arranged independently, in series, or in parallel. The device may be enclosed in an acoustically transparent shield filled with water. A torpedo-shaped shield is described, adapted to be suspended from a boat and towed, means being provided whereby an operator in the boat can rotate the enclosed detecting-device.