Patent GB-146190-A (GB)
Title: Improvements in and relating to devices for detecting and determining the direction of sounds
IPC: G01S1/72
Filed: 1920-06-25
Abstract: 146,190. Steward Davit & Equipment Corporation, (Assignees of Hayes, H, C.). June 25, 1919, [Convention date]. Detecting and locating subaqueous sounds. - Sounds are picked up by a row of microphones 1 - - 12, Fig. 1, mounted at intervals in the interior of a long flexible towing-body 51, Fig. 2. By means of a compensating-apparatus 13, the total-sound is delivered to the ear after introducing an adjustable progressive time-lag between the components transmitted by the different microphones. By this means, all the component sounds may be made to affect the ear in phase with one another, whatever direction the sound comes from, and the setting of the compensator to produce this effect indicates the direction of the sound. When the compensator has been set for a particular direction, sounds from that direction are heard with maximum intensity, while sounds from any other direction are heard more weakly, the components arriving out of phase, with one another and interfering. The detcrmination of direction is ambiguous as regards which side of the line of microphones the sound arrives from, but this ambiguity may be removed by employing two parallel lines of microphones, with the units of both lines connected to a compensator. The microphones 1 - - 6 may deliver their sounds to one ear and the microphones 7 - - 12 to the other, in which case the natural binaural sense of direction is also brought into play, the sound appearing to move from the left side of the listener's head to the right, or vice versa, as the compensator is moved through its correct position. In the form shown in Fig. 1, the microphones 1 - - 12 aro connected' to telephones 1<a> - - 12<a> and the compensator consists of a pivoted bar 20 which controls the lengths of telescopic air-tubes 1<c> - - 12<c> between the telephones and ear-pieces 24, 25. Alternatively, the compensating air-paths may consist of grooves in rotatable disks, or the time-lag may be introduced electrically in circuits connecting the microphones to the telephones of a head-set. The microphones are incorporated in a long rubber tube 51, Fig. 2, which is towed some distance behind the ship. This tubular detector is of neutral buoyancy, is kept down if necessary by weights in the towing-cable 53, and is provided with a light upper tail-fin 61 and a heavy lower tail-fin 62 to prevent rolling. Each microphone is housed in a casing 70, Fig. 4, which is gripped in the rubber tube 51 by the engagement of a rib 74 with recessed flanges 72, the fastening being secured by an external metal band 75. In assembling the detector, the tube 51 is expanded by a vacuum jacket while the microphone units are put in position, is stretched while the metal bands are slid on, and finally is filled with water. The casing 70 is of rubber. with a cylindrical metallic lining 80, Fig. 8, gripped by a band 86. The thick end 81 has a metallic support 82 moulded in it, into which the microphone is screwed; the other end is closed by a rubber plug 103 expanded by compression between plates 101, 102. The microphones, Fig. 10, are of the inertia type, one electrode 90 being carried by the stem 91 while the other electrode 95, together with the casing 92, is supported by the pair of mica diaphragms 93, 94. All the microphones of the series must be carefully matched as regards time-constant and sensitivity. The Specification as open to inspection under Sect. 91 (3) (a) describes a row of spaced micro. phones mounted in a ship's side. This subjectmatter does not appear in the Specification as accepted.