Patent GB-622097-A (GB)
Title: Improvements in devices for determining the direction of origin of a sound
IPC: G01S1/72
Filed: 1945-03-19
Abstract: 622,097. Locating and measuring sounds and like vibrations. INTERVAL INSTRUMENTS, Inc. March 19, 1945, No. 6921. Convention date, Feb. 26, 1944. [Class 118 (ii)] In a sound direction-finding system the sound is received at a plurality of spaced stations with each of which is associated a recording device, a play-back device, means for moving said play-back devices and means for simultaneously reproducing the sounds from the various play-back devices. When the reproduction of the sounds from the various play-back devices has been synchronized an indication is automatically given of the direction of origin of the sound. In one embodiment, said to be applicable to a sudden sound, e.g. from a gun, the sound is received by three microphones 50 (Fig. 3) to operate chisel-ended recording magnets 32 and so produce local magnetization on the recording wires 18 wound on discs 15, 16, 17, which are driven at a fixed speed by a synchronous motor 40 (Fig. 1). Sound is reproduced in earphones 68, 72 (Fig. 3), by play-back magnets 22, 28, 28, of which magnet 22 is fixed and the other two are mounted on discs 24 movable in the direction of travel of the recording wires. Ganged switches 52, 52a, 52b are moved to the upper, or playback, position and the magnet 28 of the disc 15 connected to earpiece 68, and magnet 22 to earpiece 72 by means of switch 71. The sounds reproduced from discs 15 and 16 are then synchronized in the ear-pieces by moving the disc 24 associated with disc 15 and a similar process is repeated for discs 16 and 17. The accurate movement of disc 24 is accomplished by means of stems 48 connected to the discs 24 by wires 45 to which are clamped posts 86. On top of the two posts 86 and a fixed bearing 81, which are of the same configuration as the microphones 50, rests a plate 82 bearing a mirror 83 by means of which an eyepiece 101 views graduations in a dial 100. The posts 86 move in agreement with the discs 24 and since the synchronizing movement of these discs (with their play-back magnets) is a measure of the time interval between the reception of sound impulses at the different microphones, so is the position of the posts 86, and so, therefore, is the direction of tilt of the mirror 83. Thus the graduations seen through the eyepiece 101 show the direction of origin of the sound. If the received sound is of non-standard velocity, the mirror will still tilt in the same direction but to a greater or less extent. The recording wires may be finally wiped clean of local magnetizations by energizing magnets 36 via switch 110 (Fig. 3). Several different sounds may be separately identified and located. A second embodiment, said to be applicable to a continuous sound, e.g. from a submarine, has a slot 186 (Fig. 6) in a dial 182 through which projects a handle 187 of a stem 173 (Fig. 5), which is rigidly clamped to a plate 174. Four posts 161, in a similar configuration to four microphones 121, are forced up against this plate by springs 164 and pull play-back magnets 129 against the action of springs 151. A switch 132 allows any two pairs of reproductions to be heard in ear-phones 139, 140, the switch being operated to produce the greatest time interval between the sounds heard in the two ear-pieces. The stem 173 is then set to an inclination according to the estimated velocity of the received sound, and the dial 182 rotated causing the stem 173 and plate 174 to rotate about a vertical axis, while the plate remains inclined to the horizontal. The height of the posts 161, and hence the position of the play-back magnets, will therefore vary as the dial is rotated, until a point is reached when the sounds in the ear-pieces will be in synchronism, when a pointer 185 indicates on the dial the direction of origin of the sound. If exact synchronism is not so obtainable, the tilt of the handle 187 may be altered slightly and the dial again rotated slightly. The number of microphones may be other than four. The wiping magnets are energized continuously.