水声无源材料插入损失测量时反聚焦方法

Measurement of insertion loss for underwater acoustic passive materials with time reversal technique

提出了利用时间反转（时反）聚焦技术的水声无源材料插入损失测量方法。通过无试样及有试样情况下实现接收信号的时反聚焦，并对聚焦信号进行透射系数计算，获得试样的插入损失。由于时反原理可实现接收信号的空时聚焦，从而提高测量信混比，因此本方法适用于非自由场环境下材料声学参数的测量，尤其适用于低频条件下的声学参数测量。波导水池试验开展了对两块试样的测量，试样尺寸为1．1m×1．0m×5mm，测量频率范围为1—20kHz，通过测量值与理论值的对比验证了该方法的有效性。

A method using time reversal （TR） technique to measure the insertion loss of passive materials is presented. To measure the insertion loss with this approach, the received signals are firstly focused according to the TR theory when a sample is not placed between the source and the received array. Then, the sample is placed near the received array and the TR processing is again employed to realize the focus of the received signal. Finally, the insertion loss of the sample is evaluated with these focusing signals. Because the TR processing can focus the energy in spatial domain and time domain, the method can be used to measure acoustic properties of passive materials with reflections induced by boundaries or low frequency sources. Two samples with the same size of 1.1 m×1.0m×5 mm are tested in a wave guide tank. The method is demonstrated by the comparison of the theoretical and the experimental results with the measured frequency range of 1-20 kHz.