Diesel engines for on highway trucks must pass noise requirements during drive by tests. The oil pan area is a major contributor to noise, and an oil pan cover/sound barrier is a way to reduce this noise. A method for producing these covers is described which involves a two stage reaction injection molding process with a composite foam liner molded in place and bonded to a barium sulfate filled outer shell. Both materials are molded at the same time during the reaction injection molding process, and one complete part is produced every machine cycle. Drive by tests show that these covers are as effective as previously used sound covers produced by more costly casting processes.