Patent ID: 7625417

Claim:
A filter screen structure, comprising a filter screen having a plurality of air vents evenly distributed thereon; and at least one impedance material being attached to said filter screen at predetermined positions to regulate a flow of air passing through said filter screen via said impedance material, wherein said filter screen is corrugated to include a plurality of corrugations, and wherein the at least one impedance material has a planer shape including a plurality of air vents, wherein the air vents of the impedance material are spaced further apart from one another than are the air vents of the filter screen, such that a density of the air vents of the impedance material is less than a density of the air vents of the filter screen; and wherein a partial area of one side of said filter screen is partially covered by said planer-shaped impedance material, and a different partial area of an opposite side of said filter screen is partially covered by said planer-shaped impedance material.