Patent ID: 7201253

Claim:
Assembly for sound-proofing in particular a motor vehicle, comprising four superimposed layers constituted respectively by: a first pair of sound-absorbing layers having a sound-absorbing property and structured to perform a sound-absorbing function, the first pair of layers comprising a first layer which has a resistance to air passage of between 500 and 2,000 N.m −3 .s, a second layer which is porous, of the acoustically resilient member type and has a resistivity of between 10,000 N.m −4 .s and 50,000 N.m −4 .s, the first layer covering the second layer, a second pair of spring-mass layers having a sound-insulating property and structured to perform a sound-insulating function, the second pair of spring-mass layers comprising a third layer which is viscoelastic, airtight, of the heavy mass type and has a density greater than or equal to 1,500 Kg/m 3 and a surface mass of between 0.2 Kg/m 2 and 9 Kg/m 2 , the second layer covering the third layer, a fourth layer which is porous, of the acoustically resilient member type and has a resistivity of between 10,000 N.m −4 .s and 50,000 N.m −4 .s, the third layer covering the fourth layer, the third layer being connected to the second layer.