The invention provides a panel section having an internally disposed open region concealed by a flexible member possessing sufficient porosity to be permeable to a flow of air therethrough. The panel section may be made by cutting an opening from an acoustical ceiling tile panel and then covering the...http://www.google.es/patents/US5533306?utm_source=gb-gplus-sharePatente US5533306 - Construction panel sections with concealed open regions
Construction panel sections with concealed open regions
