ACOUSTIC ABSORBING MEMBER WITH DIFFERENT TYPES OF PORES

摘要

An uncured acoustic absorbing member comprising a thermally inert carrier lattice comprising walls and cells between the walls defining an open lattice area, the walls being at least partly covered with a layer of an uncured thermally expandable material which cures and expands by foaming when heated to a temperature in the range of 140 to 200 0C to form nodules of a cured closed cell foam, characterized in that: a) the expansion ratio E of the thermally expandable material on heating, and b) the ratio of the open lattice area and the thickness of the layer of the uncured thermally expandable material are selected in such a way that, after foaming, the nodules come partly into contact with one another forming an arrangement of open pores between the nodules, wherein the area ratio, measured in a planar cross section perpendicular or parallel to the walls of the carrier lattice, of the open pores to the total area covered by the open pores and the nodules of the cured closed cell foam is in the range of 2 to 50 %. The member after curing and a vehicle containing the cured member are also comprised by the invention. Preferably, the cured closed cell foam has a sound absorption a at the first absorption peak in the direction of increasing frequency of at least 30 %.