Varying the Polyurethane Foam Ratio for Better Acoustic Performance and Mass Savings

Flexible molded polyurethane foams are widely used in automotive industry. As porous-elastic materials, they can be used as decoupler layers in conventional sound insulation constructions or as sound absorbers in vehicle trim parts. Flexible molded polyurethane foams are produced by reacting of liquid Isocyanate (Iso) with a liquid Polyol blend, catalysts, and other additives. Their acoustic performance can be changed by varying the mixing ratio, the weight proportion of two components: Iso and Polyol. Consequently, the sound insertion loss (IL) of barrier/foam constructions and acoustic absorption of a single foam layer will vary. In this paper, based on one industry standard flexible molded polyurethane foam process, the relationship between foam mixing ratio and foam acoustic performance is studied in terms of IL and sound absorption test results. Moreover, considering that mass saving is becoming more and more important in vehicle sound package development, the study specifically focuses on comparing the mass savings potential of different mixing ratio foams using Statistical Energy Analysis (SEA) predictions and measurement results. Finally, it is shown that lower mixing ratio foams can achieve higher IL and save mass. This was validated by one inner dash mat acoustic development application.