Abstract: The invention relates to a soundproofing device for the passenger compartment of a vehicle (10), to be positioned between a sheet métal panel of the vehicle bodywork (12) and an inner trimming panel (14). The device comprises a polymer foam plate (20) impregnated with a mixture of an inorganic filler and an organic binder, the foam plate (20) being shaped so as to be in close contact with the sheet métal panel of the bodywork (12) and with the inner trimming panel (14). The invention further relates to an inner trimming System for the passenger compartment of a vehicle, comprising an inner trimming panel (14) for covering a sheet métal panel of the vehicle bodywork (12) and such a device. The invention further relates to a vehicle provided with such a System. The invention can be used in automobiles.