Tunable acoustic reflector which constructively combines and reflects two separate incident acoustic wave paths

摘要

An acoustic reflector 10, suitable for use as a reflective target for navigational aids, comprises a shell 12 arranged to surround a solid core 16 of circular cross-section having a wave speed of 840 to 1500 metres per second; the core 16 may be spherical, cylindrical or oval in shape and may be formed from silicone rubber. The shell 12 may be made from steel or glass reinforced plastic and is adapted to transmit acoustic waves incident 18 thereon into the core 16; the acoustic waves are focused before being reflected from an opposing side 20 of the shell 12 to provide a reflected acoustic wave 22. The shell 12 has at least two areas of transmissibility 19, 19' such that the waves incident 18 on the shell 12 follow separate paths within the core 16 before being re-radiated and combining constructively to provide an enhanced reflected acoustic wave 22 at one or more pre-determined frequencies.