Sound-absorbing device, especially for damping of noises expanding in air ducts

Claim 1

A sound-absorbing device for use in the transmission of ventilating air, comprising: a prismatic elongated casing having a pair of end walls and a plurality of angularly adjoining longitudinal walls; at least one air-flow duct of round cross section extending between said end walls and terminating therein while passing through said casing in all around spaced relation from said longitudinal walls; and a mass of sound-absorbing material without parallel surfaces filling said casing between said end walls and around said duct, said sound-absorbing material having a thickness around said duct as measured in each plane perpendicular thereto which varies continuously about the periphery of the duct, said casing having a square cross section in said planes and said duct having a circular cross section in said planes and being conical from one of said end walls to the other, a plurality of such ducts being provided in spaced-apart relation within said casing and being all spaced from said longitudinal walls, said sound absorbing-material surrounding each duct in each such plane, said sound-absorbing material being subdivided by plates in said casing perpendicular to said ducts.