Sound absorption coefficient measurement by extracting the first reflected wave in a short tube

Abstract

This study presents a method for measuring the normal incident sound absorption coefficients of acoustic materials by extracting the first reflected wave in a short pulse tube. Instead of generating a short pulse in a tube with an open end, the inverse filter method is used when a sample is added at the end of the tube, which makes it possible to extract the first reflected wave directly from the superposed sound field in the time domain. The length of the tube used in this proposed pulse separation method is half as long as that of the traditional pulse separation method, which makes it can be used in a general commercial impedance tube. Two different materials are investigated. When the proposed method is compared to the traditional transfer function method and the traditional pulse separation method, good agreement can be observed among these three methods.