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脉冲声源系放电装置,利用聚丙烯为绝缘材料被固定在直径9mm的铜管一端,每2s产生一个脉冲平面声波.管的另一端安装待测的试件.在计算中,实际上只要算出反射波谱同入射波谱的比值——复反射系数便可,其它参数均已知,诸如空气的特性阻抗和管径.测定中必须考虑到管中声的传播损失,实验表明此量在高频段尤为显著.利用棉纱和厚棉绒进行的三组实验所得的表面声阻抗特性,表明测定的结果是良好的.在测定中,通过平面波获得材料的声阻抗,由试件产生的部分反射波可利用时间窗加以切除,并利用FFT技术算出表面声阻抗特性.
Pulsed sound source discharge device, the use of polypropylene insulation material is fixed to one end of a 9mm diameter copper tube, every 2s to produce a pulse plane acoustic wave. The other end of the tube to be tested to be tested in the calculation, in fact, as long as the calculated The ratio of the reflection spectrum to the incident spectrum - the complex reflection coefficient, is known and other parameters are known, such as the characteristic impedance and the diameter of the air. The measurement must take into account the propagation loss of the sound in the pipe. Experiments show that this amount is especially high in the high frequency range Significantly, the surface acoustic impedance characteristics obtained from the three sets of experiments using cotton yarn and thick cotton linter showed that the measurement result was good. In the measurement, the acoustic impedance of the material was obtained by the plane wave, and the partially reflected wave generated by the test piece was available Time window to be removed, and the use of FFT technology to calculate the surface acoustic impedance characteristics.