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发展了一种测量水声材料声学性能的行波管测量技术,能够在实验室充水管中模拟海洋水温水压环境,对样品的声学参数实施低频范围的测量。被测样品置于声管中央,声管两端配置一对发射器。应用主动消声技术使样品的透射声波在声管次发射器表面的反射可忽略,在管中建立起行波声场。然后,通过分别计算样品两边声场中每一对水听器的传递函数,得到样品的反射系数和透射系数。测量系统声管的内径为Φ208 mm,工作频率范围为100～4000 Hz,最高静水压为5 MPa。对水层和层状不锈钢样品的反射系数和透射系数进行了实际测量和理论计算,结果表明,测量值和计算值有较好的吻合,测量不确定度不大于1．5 dB。
A traveling wave tube measurement technique for measuring the acoustic performance of underwater acoustic materials has been developed. It can simulate the ocean water temperature and pressure environment in a laboratory filled water pipe and measure the acoustic parameters of the sample in the low frequency range. The sample to be measured is placed in the center of the sound tube and a pair of emitters is arranged at both ends of the sound tube. The application of active noise cancellation technique can make the reflection of the transmitted sound wave of the sample on the surface of the secondary emitter of the sound tube negligible and establish the traveling wave sound field in the tube. Then, by calculating the transfer function of each pair of hydrophone in the sound field on both sides of the sample respectively, the reflection coefficient and transmission coefficient of the sample are obtained. The inner diameter of the sounding tube of the measuring system is Φ208 mm, the working frequency range is 100-4000 Hz and the maximum hydrostatic pressure is 5 MPa. The reflection coefficient and transmission coefficient of water layer and layered stainless steel sample were measured and calculated theoretically. The results show that the measured value and the calculated value agree well with the uncertainty of measurement not more than 1.5 dB.