Acoustic reflectors

摘要

An acoustic reflector (10) comprises a shell (12) surrounding a core (16), said shell (12) being capable of transmitting acoustic waves incident on the surface of the shell (12) into the core (16) to be focused and reflected from an area of the shell (12) located opposite to the area of incidence so as to provide a reflected acoustic signal output from the reflector (10), having a core (16) in which the shell (12) is dimensioned relative to the core (16) such that a portion of the acoustic waves incident on the shell wall are coupled into the shell (12) and guided therein around the circumference of the shell (12) and then re- radiated to combine constructively with the said reflected acoustic signal output so as to provide an enhanced reflected acoustic signal output. The ratio of the speed of sound wave transmission in the shell to the average speed of the wave transmission in the core is preferably in the range of 2.74 to 3.4, inclusive with best result in the range of 2.74 to 2.86 inclusive.