GB135286A - - Google Patents

Abstract

135,286. Mather, T., Irwin, J. T., Fletcher, G. H., and Webb, C. E. Nov. 19, 1918. Subaqueous audible signals.-To produce a parallel sound beam for subaqueous signalling and like purposes, a source of sound is placed at or near the focus of a concave reflector of the kind described in Specification 132,821, [Class 13, Bells &c.], having a yielding or flexible reflecting- surface mounted on a rigid back. The reflector is of the order of ten feet in diameter, and the apparatus is mounted so that it can be rotated. The reflecting-diaphragm A may be of rubber resting against annular ribs C on a rigid back B made in sections connected by flanges b, and air under pressure is admitted to the spaces between the ribs through one or more valves E. The ribs may be perforated so that the same pressure obtains all over the back surface of the diaphragm A, or different pressures may be used at different parts of the device, so that different water pressures due to depth of immersion may be compensated. Alternatively, the member A may be of metal or strong material, and a partial or high vacuum employed in the spaces between the ribs. The sound source D is supported on a tripod d and comprises a water-tight casing containing an electro-magnet d<2> excited by alternating or interrupted current and acting on a diaphragm d<1>.