Scattered field distributions from the near to the far field using an acoustic lens

An experimental technique for measuring the acoustic scattering from bodies over a range of frequencies from approximately 100 kHz to 3 MHz is described. A compact arrangement comprising a large-area piezoelectric transmitter in conjunction with an acoustic lens allows scattering measurements to be made from the near to the far field in a laboratory water tank. An approximation to plane-wave or point-source insonification is achieved by the selection of an appropriate single or compound lens, respectively. Experimental results are compared with predictions for the scattering from a cylinder insonified normal to its axis. Results are also presented for monostatic scattering from a more complex body as a function of aspect angle. The technique has been found to be useful for the validation of computer or other models of scattering and for scale-model measurements.