481 - Experimental determination of the acoustic characteristics of porous materials in a standing wave tube
Lim B., Chang H.
Abstract
Two-microphone method has been widely used as a standard test method for the determination of the reflection coefficient and acoustic impedance. The complex reflection coefficient as a function of frequency also contains the information about the wave speed and attenuation in the porous material. In this paper a signal analysis technique is developed in order to determine the wave speed and attenuation in the porous material within a frequency band. Complex reflection coefficient is modeled as a rational function and its pole-zero distribution is calculated. The poles and zeros depend on the thickness and wave speed of the porous material, and the specific acoustic impedance. Therefore the complex wave speed of the porous material can be determined from the poles and zeros. The analysis result is compared with the numerical simulation based on the micro fluid dynamics. Analysis results of experimental data by this method show good agreement with the numerical simulation.
Citation
Lim B.; Chang H.: Experimental determination of the acoustic characteristics of porous materials in a standing wave tube, CD-ROM Proceedings of the Thirtheenth International Congress on Sound and Vibration (ICSV13), July 2-6, 2006, Vienna, Austria, Eds.: Eberhardsteiner, J.; Mang, H.A.; Waubke, H., Publisher: Vienna University of Technology, Austria, ISBN: 3-9501554-5-7
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