Improvements in and relating to apparatus for ascertaining the direction of sounds

Abstract

Abstract 395,081. Locating sounds. KOLB, O. K., Lincoln Hall, Upper Bedford Place, London. March 3, 1932, No. 6458. [Class 118 (ii).] Apparatus for use on ships, lighthouses, and buoys for determining the direction of sound signals comprises a long, narrow microphone 6, or a number of microphones arranged in a line, located at or near and parallel to the focal line of a rotatable reflector 4 having a straight generating line and parabolic or other cross section, the arrangement being such that only sound waves passing in a given direction are reflected, and reflected once only, on to the microphone. The width of the microphone does not exceed one-tenth of the length of the line joining the points 1, 2 of the reflector. Baffles 10, 11 may be provided. Fig. 4 shows a cruciform reflector 4<1>, 4<11> with a cruciform microphone 6a, the whole unit being tiltable both about a horizontal and a vertical axis to obtain the maximum sound effect and thus ascertain the direction of transmission. The cruciform microphone may be divided into vertical and horizontal components located at or near the different focal lines of the two reflectors. In another modification, Fig. 3, two reflectors 4<1>, 4<11> are arranged at right-angles to one another, one above the other, each having its own microphone 6<1>, 6<11>. For preventing other sound waves acting on the microphone 6, Fig. 6, the reflector 4 is fitted with a casing 7 having corrugations 8, 9 of sponge rubber, felt, or other sound-absorbing material. The top and bottom walls of the casing may have their inclination adjustable. Baffles 10, which may be adjustable about a vertical axis, may also be provided. Fig. 7 shows horizontal baffles 11 adjustable about horizontal axes. In a tubular apparatus 14, Fig. 10, the microphone 6 is protected from wind and eddy currents by a gauze front 15 having a solid nose 16, and additional gauze screens 17, 18, 19. Devices for rotating the reflector and microphone, either directly or through chan gear, are described. Fig. 1 shows the circuit of a thermionic valve 28 and loud-speaker 33, a meter 34 in the plate circuit of a valve 35 indicating the loudness of the sounds received and amplified. For excluding undesired signals, the microphone or output circuit may include one or more electric filters for passing required frequency ranges only.

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