Patent ID: 7059089

Claim:
A tensioned structure comprising a flexible sheet of material having a thickness less than half a millimeter and tensioned relative to a support means; the material including microprojections formed by displacing the material from which it is made, said material presenting an acoustic absorbtion coefficient which is higher than that of the same material without said projections; the height (h) of the microprojections measured in a direction perpendicular to the plane of said sheet in the vicinity of said microprojections is less than three times the thickness of said sheet; the microprojections project from both faces of said sheet; each microprojection is located at a node of a regular pattern; all of the microprojections are disposed at the nodes of a single pattern; the pattern has a square mesh; the microprojections are in the form of depressions having a substantially plane end wall connected to an opening via a strip of material of thickness that is smaller than or equal to the thickness of portions of the sheet between the microprojections; the depressions are circularly symmetrical about respective axes that are substantially perpendicular to their end walls; the strip of material connecting the end wall of a depression to its opening is discontinuous; it is provided with microperforations, having openings smaller than four-tenths of a millimeter; at least a fraction of the microprojections are provided with said microperforations or said microperforations are disposed between the microprojections.