GB146189A - Improvements in method of and apparatus for directive sound transmission - Google Patents

Abstract

146,189. Steward Davit & Equipment Corporation, (Assignees of Hayes, H. C., and Mason, M.). June 25, 1919, [Convention date]. Subaqueous audible signals.-Sound is transmitted in any desired direction by means of a number of sources which are spaced apart and operate in a definite controllable phase-relationship to one another. In the form shown in Fig. 1, electro-magnetic transmitters 1 - - 12, constructed as shown in Fig. 3, are fed from a common supply alternator 20 through time-lag circuits 21, 22, &c., consisting of inductances in series and capacities in parallel, by means of which their relative phases can be controlled. For example, the transmitter 1 is fed through the left-hand branches of circuits 21, 22, 24; the transmitter 2 through the left-hand branches of circuits 21, 22 and circuit 28; the transmitter 3 through the left-hand branches of circuits 21, 22 and the right-hand branch of circuit 24; and so on. The switches 46, 49, &c., which determine the points at which the .current branches through the different circuits, are connected so as to move in unison. When these switches are in their central positions, the current arrives at all the transmitters in phase, and sound is propagated in a direction at right-angles to the line of transmitters, but when the switches are moved to one side or the other progressive phase-differences are introduced between the different transmitters and sound is propagated obliquely, as indicated by the dotted lines. To minimize reflection in the circuits, the impedance of each branch is arranged to be approximately equal to that of the branched circuit into which it divides. The switch 46 is of a two-contact type, arranged to open the time-lag circuit between the two contacts. This is of advantage when the installation is used for directional reception; by throwing a switch 42 the telephones 70, 71 of a headset are connected in place of the alternator 20, and the direction of a received sound can be determined by both the maximum-intensity and binaural effects. The transmitters may be on board ship or on a shore station; they may be in a circle instead of in a line, and may be separately excited instead of from a common alternator ; they may be of non-electric type, the sounds being transmitted through air-columns of variable length. Specifications 146,188 and 146,193 are referred to.