A Directional Hydrophone Having a Favourable Hydrodynamical Shape in Analogy to the Dielectric Rod Radiator

A description is given of a directional hydroacoustic axial radiator using a conical rod filled with a fluid of low sound velocity which is coupled with a piston transducer. Analogously to the dielectric rod radiator in radar technique a guided surface wave propagates along the rod which is radiated reflectionless into the direction of the tapering.

For the application in streaming water it appears to be favourable that the geometrical cross-section is smaller about one to two orders of magnitude than that of aperture radiators of equal directivity.

Half-width and side lobe suppression as functions of rod length and frequency are investigated experimentally for several filling fluids.