perforated plasterboard ceiling panels shatter echo in a large hall with tiled floor. entrance hall in a

white wall undefined theatre surround surface square sprinkler sounds soundproof sound skylight site school ribbed restaurant reduction reduce recessed porous plasterboard perforated office noise muted mute light interior insulation installation industrial halogen hall grid greenery gray grass fire fence echo drywall dots design cover construction conditioning concert close cellulose ceiling cafeteria bulb auditorium application air acoustic