Effect of Fiber Cross Section Shape on the Sound Absorption and the Sound Insulation

Abstract

The car uses a variety of porous materials such as PET nonwoven felt, urethane foam and glass wool to prevent noise from entering the cabin room while driving. Among them, PET felt is most commonly used for advantages such as economic feasibility and moldability. Factors related to the noise reduction performance of PET felt include surface area weight, thickness of fibers, type of scrim, and needling process etc. Among them, this study conducted and compared the sound absorption and sound insulation performance on the cross section shape of the fibers that make up the nonwoven felt. Changing the cross section shape of the fiber means that the specific surface area of the fiber changes. Acoustically, sound absorption is the process in which sound waves cause friction with the medium surface of porous material and then convert it into thermal energy. Therefore, as the specific surface area of the fiber changes, the effect of absorption is also changed. In this study, it can identify the change in noise reduction effect on the fiber cross section shape through five types of fibers with different cross section shapes. The five types of fibers had different shape factor and specific surface area. As a result of different cross section shape, it showed the difference of sound absorption performance. The sound absorption performance was shown in a similar order to the order of specific surface area. However, when it comes to sound insulation performance, the effect of specific surface area was limited. It can be concluded that the sound insulation performance is mainly affected by the weight and stiffness of the test piece.