Acoustic foam decoupler
A noise attenuating trim part for a vehicle, with acoustic mass-spring characteristics comprising a mass layer comprising at least an impervious barrier layer, and a decoupling layer consisting of open cell foam and wherein the decoupling layer has a first surface adjacent to the mass layer and a second surface facing away from the mass layer, and wherein the decoupling layer and mass layer are laminated together and wherein the decoupling layer has at least one region with a plurality of indentations wherein each indentation comprises a round base area wherein the round base areas are situated in plane with the second surface and wherein the total surface area of the round base areas is between 10 and 40% of the total surface area of the second surface of the decoupling layer.
1. A noise attenuating trim part for a vehicle, with acoustic mass-spring characteristics, comprising:
a mass layer having an impervious barrier layer;
a decoupling layer comprising open cell foam, the decoupling layer having a first surface laminated to the mass layer and a second surface facing away from the mass layer and adapted for interconnection to a vehicle body, wherein the second surface includes
at least one region with a plurality of indentations, and
wherein each indentation is defined by a geometric shape bounded by a generally round base area that corresponds with the second surface, such that the entirety of the round base areas are configured to contact the vehicle body and the geometric shapes define cavities between the decoupling layer and the vehicle body;
wherein the total surface area of the generally round base areas is between 10 and 40% of the total surface area of the second surface of the decoupling layer; and
wherein a shortest distance (D) between two indentations is more than 4 mm.
2. The noise attenuating trim part according to claim 1 , wherein the radius (r) of the generally round base areas is between 4 to 20 mm.
3. The noise attenuating trim part according to claim 1 , wherein the total surface area of the base areas is between 15 and 35% of the total surface area of the second surface of the decoupling layer.
4. The noise attenuating trim part according to claim 1 , wherein the height (h) of the indentations is between 40 and 74% of the total thickness (T) of the decoupling layer being the shortest distance from the base area of the indentation to the first surface of the decoupling layer.
5. The noise attenuating trim part according to claim 1 , wherein the height (h) of the indentations is between 4 to 20 mm.
6. The noise attenuating trim part according to claim 1 , wherein the decoupling layer includes a convex portion that defines the at least one region with a plurality of indentations, and wherein the region has at least 15 indentations and wherein the total surface area of the generally round base areas within the at least one region is between 25 and 50% of the surface area of the at least one region.
7. The noise attenuating trim part according to claim 1 , wherein the decoupling layer is made of polyurethane foam.
8. The noise attenuating trim part according to claim 1 , wherein at least one of the generally round base areas has an elliptic shape.
9. The noise attenuating trim part according to claim 1 , wherein at least one of the indentations has the geometrical shape of a hemi spheroid.
10. The noise attenuating trim part according to claim 9 , wherein the hemispheroid shape with a profile adjacent to the second surface is cylindrical, perpendicular to the second surface, and bounded by the round base areas.
11. The noise attenuating trim part according to claim 1 , wherein the foam has a density between 25 to 100 kg/m 3 .
12. The noise attenuating trim part according to claim 1 , wherein the impervious barrier layer is made of a thermoset plastic material selected from the group consisting of ethylene vinyl acetate (EVA) copolymer, polyester, polyethylene terephthalate, high density polyethylene, low density polyethylene, linear low density polyethylene, polypropylene, thermoplastic elastomer, thermoplastic rubber and polyvinyl chloride (PVC), or any combination thereof.
13. The noise attenuating trim part according to claim 1 , wherein the mass layer has an area weight between 500 to 6500 g/m 2 .
14. The noise attenuating trim part according to claim 13 , wherein the mass layer consists of the impervious barrier layer with an area weight between 800 to 6000 g/m 2 .
15. The noise attenuating trim part according to claim 14 , further comprising an additional layer adjacent to the mass layer, wherein the additional layer is made of porous felt with an area weight of 200 to 600 g/m 2 or open cell foam.
16. The noise attenuating trim part according to claim 13 , wherein the mass layer consists of the impervious barrier layer and a porous fibrous layer;
wherein the porous fibrous layer has a dynamic compression Young's modulus E of at least 96*AW* t p (Pa), with AW area weight (g/m 2 ) and t p thickness (mm) of the porous fibrous layer;
wherein the impervious barrier layer has an area weight of less than 200 g/m 2 ; and
wherein the impervious barrier layer is situated between the fibrous layer and the decoupling layer and all layers are laminated together.
17. The noise attenuating trim part according to claim 16 , wherein the mass layer has an area weight between 500 to 2600 g/m 2 .
18. The noise attenuating trim part according to claim 13 , wherein the mass layer consists of the impervious barrier layer and a porous fibrous layer, with the impervious barrier layer being situated between the porous fibrous layer and the decoupling layer and all layers are laminated together, and
wherein the porous fibrous layer has a dynamic compression Young's modulus (Pa) of at least 118* t p *(AW b *AW p +(AW p *AW p /4))/(AW b +AW p );
wherein AW b being area weight (g/m 2 ) of the barrier layer, AW p being area weight (g/m 2 ) of the porous fibrous layer, t p being thickness (mm) of the porous fibrous layer; and
wherein the impervious barrier layer has an area weight of at least 500 g/m 2 .
19. The noise attenuating trim part according to claim 18 , wherein the impervious barrier layer has an area weight between 500 to 4000 g/m 2 ; and
wherein the porous fibrous layer has an area weight between 400 to 2500 g/m 2 .
20. The noise attenuating trim part according to claim 16 , wherein the thickness t p of the porous fibrous layer is between 2 and 15 mm.
21. The noise attenuating trim part according to claim 1 , further comprising at least one of a decorative layer or a carpet layer, and wherein the mass layer is situated in between the decoupling layer and the decorative layer or carpet layer.
22. The noise attenuating trim part according to claim 1 , wherein the plurality of indentations comprise at least one of indentations of a first size and indentations of a second size, and indentations of a first shape and indentations of a second shape.
23. The noise attenuating trim part according to claim 1 , wherein the plurality of indentations are not equally spaced from each other.
24. The noise attenuating trim part according to claim 1 , wherein the plurality of indentations are randomly spaced.
25. The noise attenuating trim part according to claim 1 , wherein the compression stiffness of the foam is comprised between 4 kPa and 20 kPa, being the compression stiffness corresponding to the CLD40 value measured according to ISO 3386-1.
26. The noise attenuating trim part according to claim 1 , wherein the second surface is selectively deformable and adapted to engage a vehicle body having an irregular surface.
27. A method of using the noise attenuating trim part according to claim 1 , as a floor covering or inner dash, wherein the second surface of the decoupling layer with a plurality of indentations is facing the vehicle floor and or firewall.