Reducing automotive interior noise with natural fiber nonwoven floor covering systems

Eliminating unwanted noise in passenger compartments of vehicles is important to automobile manufacturers. The ability to reduce noise inside the vehicle enhances the perceived value of the vehicle to the consumer, and offers a competitive advantage to the manufacturer. Several methods are presently employed to reduce noise and its sources, one of which uses sound-absorbing materials attached to various components such as floor-coverings, package trays, door panels, headliners and trunk liners. Natural fibers are noise-absorbing materials that are renewable and biodegradable, making them an effective choice for the automobile industry. Floor coverings using natural fibers (kenaf, jute, waste cotton, and flax) in blends with polypropylene (PP) and polyester (PET) were developed as carded needle-punched nonwovens. The acoustical absorption coefficients of these floor coverings, and of floor coverings in combination with an underpad (either a rebonded polyurethane foam, or a soft cotton nonwoven) were evaluated by ASTM E-1050 in the frequency range of 100 to 3200 Hz. By stacking an underpad and a floor covering together, a floor covering system was created. The measurements demonstrated that each of the natural fiber-based nonwoven floor coverings contributed to noise reduction, e.g., coefficients = 0.54-0.81 at 3.2 kHz. Noise was significantly reduced with a floor covering system using either of the underpads. The most reduction occurred with a polyurethane pad; for example, for kenaf floor covering C20-1. the coefficients at 3.2 kHz were: 1.0 with polyurethane versus 0.81 with cotton pad.