Abstract: The invention provides an acoustical attenuator comprising:a porous material comprised of particles sintered and/or bonded together at their points of contact, having at least a portion of pores continuously connected, wherein said porous material has an interstitial porosity of about 20 to about 60 percent, an average pore diameter of about 5 to about 280 micrometers, a tortuosity of about 1.25 to about 2.5, a density of about 5 to about 60 pounds per cubic foot, a modulus of about 12,000 pounds per square inch or above, wherein said porous material has at least one through hole and wherein said interstitial porosity, average pore diameter, density and modulus values are for the porous material in the absence of any through holes, wherein the average diameter of the through hole is greater than the average pore diameter.

Abstract: An electromagnetic radiation suppression covering conformable to a corresponding selected structure through reducing the extent of a surface dimension therein and containing one or more absorptive kinds of particles in a sheet of a corresponding thickness including such particles as iron oxides with adsorbed surface layers, such covering being formed through extruding a mixture of selected particles and binding material.