The invention relates to an acoustic and thermal shield (1) for a motor vehicle, the shield comprising a porous shell (2) based on fibres bound together by a binding agent and a spring layer (3) based on elastically compressible polyurethane foam, the porosity of the shell being such that the foam is able to create a sealed skin (5) on the underside of the shell, which fibres consist of two types: thick reinforcing fibres in an amount of 25 to 40% by weight of the shell and fine fibres in an amount of 15 to 35% by weight of the shell, the bonding agent being formed by fusible bonding fibres in an amount of 35 to 50% by weight of the shell, so that substantially no foam penetrates the thickness of the shell.