Dear Alvin Kissoondoyal, if it has such a shielding effect it will help and contribute in sound isolation. The main effect is that of PU bulk structure. My Regards

Dear Alvin Kissoondoyal, if it has such a shielding effect it will help and contribute in sound isolation. The main effect is that of PU bulk structure. My Regards

Alvin Kissoondoyal Mold release and surfactant can affect air permeability, which affects sound absorption (there's a sweet spot -- you don't want too little air permeability, you don't want too much), so you can start there.

You can do tests on the airflow resistivity of samples with and without the agents and compare to model calculations of the absorption based on measured input. Or do the absorption measurement directly on samples in a tube or in a reverberation room using larger samples. In general the automotive absorbents are too thin, or they will benefit from some airspace behind them.