VENTILATION DUCT INCLUDING SOUND DAMPNING MATERIALS WITH DIFFERENT DENSITY AND A VALVE

摘要

The present invention relates to a ventilation duct that comprises a casing (1; 101) that on its interior is covered with a sound absorption material (9, 10; 109, 110). According to a preferred embodiment of the invention a damper (20; 120) is provided inside the ventilation duct. It is significant of the ventilation duct of the present invention that sound absorption material (9, 10; 109, 110), having at least two different densities, is provided inside the casing (1; 101), and that the sound absorption material (10; 110) having the lowest density defines an air flow area, said sound absorption material (10; 110) constituting the surface layer inside the ventilation duct.