GB/T 18696.2-2002 in English

《GB/T 18696.2-2002声学 阻抗管中吸声系数和声阻抗的测量 第2部分:传递函数法》由TC17（全国声学标准化技术委员会）归口，主管部门为中国科学院。
传递函数法测定法向入射条件下吸声材料的吸声系数，涉及阻抗管的使用、两个传声器的位置和数字频率分析系统。本方法也能用来测定吸声材料的表面声阻抗率或表面声导纳率。由于吸声材料的声阻抗率与它的物理特性（诸如流阻、孔隙率、弹性模量和密度）有关，所经本标准规定的测量方法在有关的基础研究和产品开发方面也有用处。

Scope

The transfer function method is used to determine the sound absorption coefficient of sound-absorbing materials under normal incidence conditions, involving the use of impedance tubes, the location of two microphones and a digital frequency analysis system. This method can also be used to determine the surface acoustic resistivity or surface acoustic admittance of sound-absorbing materials. Since the acoustic impedance of sound-absorbing materials is related to its physical properties (such as flow resistance, porosity, elastic modulus and density), the measurement methods specified in this standard are also useful in related basic research and product development. This method is similar to the method stipulated in ISO 10534-1. An impedance tube with one end connected to the sound source and the other end to install the test piece is used, but the measurement method is completely different. In this method, the plane wave in the pipe is generated by the noise source, and the analysis of the interference field is realized by measuring the sound pressure at two points with two microphones installed at a certain position on the pipe wall (or a microphone that can move in the pipe). , and then complete the calculation of the complex transfer function, the normal incident sound absorption coefficient and the acoustic impedance rate of the sound-absorbing material. The purpose of this method is to provide another measurement method which is faster than the standing wave ratio method. Comparing this method with the sound absorption measurement method of the reverberation room stipulated in ISO 354, it can be seen that there is a big difference between the two. (Under ideal conditions) The reverberation chamber method is used to determine the diffuse incident sound absorption coefficient, which can be used to test materials with significantly different structures in the transverse and normal directions. However, the reverberation chamber method requires a larger test sample, which is inconvenient for the research and development of sound-absorbing materials that can only provide small samples. The impedance tube method is limited to the study of normal incidence parameters, requiring the test sample to be as large as the cross-section of the impedance tube. For locally reacting materials, the diffuse incident sound absorption coefficient can be estimated from measurements obtained by the impedance tube method. The algorithm for converting the test data of impedance tube method (normal incidence) to the corresponding results of diffuse incidence is shown in Appendix F