Abstract: An improved acoustical material, which is simple in construction and uses conventional, inexpensive materials, for use as a lining material in association with noise generating machinery is disclosed. It comprises two woven fiberglass layers and an intermediate non-woven fibrous layer to form a composite which will not deteriorate, swell or retain oil, solvents, or water such as are found in machinery, and which has acoustical flow resistance of between 20 rayls and 80 rayls. The flexible composite may be used over a highly porous layer which is or acts as a dead air space relative to the composite.

Abstract: An improved acoustical material, which is simple in construction and uses conventional, inexpensive materials, for use as a lining material in association with noise generating machinery, comprising, in combination, a composite layer of plural layers of porous material which will not deteriorate, swell or retain oil, solvents, or water such as are found in machinery, and which has acoustical flow resistance of between 20 rayls and 80 rayls, and a highly porous layer which is or acts as a dead air space relative to the composite.