| Popis: |
A method of measuring the echo reduction of passive materials based on inverse filtering technique is presented. In this method, a received signal which contains circuit channel and underwater acoustic channel information is obtained by transmitting the initial pilot signal and receiving signals through the hydrophone. With inverse filtering technique, the channel transfer function between the transducer array and hydrophone can be calculated. Then, the inverse function of the transfer function can be obtained by a robust inversion method. By retransmitting the inverse function, the spatial and temporal pulse focus at the position of the hydrophone is achieved. Simulation examples of the inverse filtering show its high performance at the pulse compression and reverberation suppression. A steel plate sample with the size of 1.2m×1.6m×0.028m is tested in a wave guide tank. The method is demonstrated by the comparison of the theoretical and the experimental results in the measured frequency ranges from 1 to 5 kHz. |
