Abstract: The process for the production of double-walled mouldings for the reduction of sound in vehicles and engines in general by means of a single pressing operation consists in introducing into a compression mould a double package, each individual package consisting of a layer of prepolymer fibres and a foil of thermoplastics material. The foils of the individual packages are situated facing one another and a medium under pressure is blown in between these foils, in order to cause each package layer to be pressed against the internal face of the corresponding half-mould. The compression mould is heated to a temperature which is sufficient to cause complete melting of said foil and complete polymerization of said prepolymer fibres.