Patent ID: 8770345

Claim:
An acoustical panel for forming a ceiling or wall, the panel extending across a rectangular area with a nominal thickness of about at least ½ in., the panel having a core made primarily of gypsum, the core being essentially coextensive with the panel area such that it has two opposed sides each of an area substantially equal to the area of the panel, the core having a multitude of perforations extending generally between its sides, the perforations being distributed substantially uniformly across the full area of the core and being open at face and rear sides of the core, the face side of the core being covered by an effectively visually imperforate porous layer when painted, the perforations being restricted by a porous covering at a rear side of the core, the porous layer at the face side of the core being suitable for adherence by conventional drywall joint compound and a water-based non-blocking paint, the panel, after the porous layer at the face side of the core and joint compound are painted with said non-blocking paint, being adapted to exhibit an NRC of 0.50 or more.