Automotive insulating trim part

A sound insulating trim part with acoustic mass-spring characteristics comprising a mass layer (A) and a decoupling layer (B) (3) , characterised in that the mass layer (A) consists of a porous fibrous layer (1) with a dynamic Young's modulus (Pa) of at least (96¢AW¢t) with AW area weight (g/m 2 ), and t thickness (mm) of the fibrous layer (1), and an air impermeable thin barrier layer (2) between the fibrous layer (1) and the decoupling layer (3).