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Development Research on Measuring Method of sound propagation Constants of Porous Materials.

多孔材料声传播常数测量方法的开发研究。

基本信息

批准号：
06555172
负责人：
IWASE Teruo
金额：
$ 4.22万
依托单位：
Niigta University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Developmental Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

项目摘要

Porous materials such as glass-wool and rock -wool, are famous and useful as acoustical materials. There are two important acoustical parameters of sound absorption coefficient and sound propagation constant. It is easy to measure former one by using sound tube method or reverberation room method. On the other hand, it is recognized that it is very difficult to measure after propagation constant.Therefor, head investigator had proposed a new measuring method for propagation constant. By this method, there could not be necessity of any air space, which caused difficulty in ordinary method, back of test material positing at sound tube end. The new method based on digital signal processing technique. Propagation constant could be easily obtained from trabsfer function between sound pressures in front of test material and back of that.The purpose of this project is the development the new measuring method.After consideration, We made the measuring system that sound tube could be divided to tree parts. Before sound measurement, easy re-connection with air-tight could be made. The measuring system is possible for the acoustical impedance measuring as well as propagation constant. In addition on this research, for popular porous materials, several propagation constants and sound impedance had be measured. Special measurements for particle material such as sand and soft paper, which could not be measured by except this technique, were carried out. It was found out that dB attenuation value in unit length increased with the increase in the frequency. It was also found out that sound speed in porous material was lower than the sound velocity in the air. Finally of this project, reducing of resonance of the test material could be investigate.

多孔材料如玻璃棉和岩棉是著名且有用的声学材料。有两个重要的声学参数：吸声系数和声音传播常数。前者采用声管法或混响室法很容易测量。另一方面，人们认识到传播常数之后的测量非常困难。因此，首席研究员提出了一种新的传播常数测量方法。通过这种方法，不需要任何空气空间，而这会造成普通方法中测试材料背面定位在声管端部的困难。基于数字信号处理技术的新方法。从测试材料前面和后面的声压之间的传递函数可以很容易地获得传播常数。该项目的目的是开发新的测量方法。经过考虑，我们制作了声管可以分为树部分的测量系统。在进行声音测量之前，可以轻松地进行气密重新连接。该测量系统可用于声阻抗测量以及传播常数。此外，在这项研究中，还测量了流行的多孔材料的几个传播常数和声阻抗。对沙子和软纸等颗粒材料进行了特殊测量，这些材料只能通过这种技术进行测量。结果发现，单位长度内的dB衰减值随着频率的增加而增加。研究还发现，多孔材料中的声速低于空气中的声速。该项目的最后，可以研究减少测试材料的共振。