Influence of Surface Discontinuity on Sound Absorption Coefficient of Vehicle Interior Material

Abstract

There has been considerable effort in the automotive industry to reduce and control the noise in the car cabin. Selecting or designing a better absorber will enhance the comfort of the passengers in the car. There are many techniques to reduce or control the noise in the car cabin. One of the techniques is to place specific material in order to reduce its acoustical noise. This paper presents a study on sound absorption of the felt, polyurethane foam and fabric which are commonly used as car interior material. Furthermore, the influence of surface discontinuity created between two joined material parts is also investigated. The sound absorption coefficient is measured using two-microphone impedance tube. This tube is used to provide noise source frequency ranging from 50 Hz to 10 kHz. Using the dBAlpha software that is connected to the microphone via Symphonie Analyzer, the sound absorption coefficient of the material for every frequency is presented in tabular as well as in graphical form. The test results show that material selection is significantly important for the absorption of noise. Besides, it is found that the surface discontinuity gives different effect depending on the material. For the felt material, the surface discontinuity has insignificant effect. However, the surface discontinuity may give a moderate effect for other materials such as polyurethane foam and fabric.