Comparison of sound insulation performance between closed-cell foam and automotive carpet

In developing sound insulation materials for automobiles, multiple sound insulation and sound absorption materials are laminated to achieve high performance. Generally, steel sheets, needle felts, and carpets are used to create sound insulation properties. In a luxury car, multiple layers with sound absorption and sound insulation properties are placed on the carpet to add higher sound insulation properties, but this increases the mass of the carpet. To solve this problem, we are investigating the the potential to realize both lightweight and high sound insulation properties using closed-cell form. In this study, we experimentally evaluated the sound transmission loss of closed-cell foam by comparing it with those of carpets with the same configuration used in standard and luxury cars.Furthermore, a numerical study is conducted. As a result, the closed-cell foam obtained higher sound transmission loss than the automobile specification carpet in a wide frequency range from 400 Hz to 5000 Hz. On the other hand, the sound transmission loss decreased by the same degree for both the automotive carpets and the closed-cell foam at 250 Hz.