Silencer for noise reduction on the intake side of roof fans. With sound attenuation baffles made of abrasion-resistant and non-combustible mineral fibre boards. Recommended accessories: SZ intermediate connection piece for connecting pipework: SD 40, Max. Flow velocity: 20 m/s, Housing material: Galvanised sheet steel, Weight: 39 kg, Weight with packaging: 39 kg, Suitable for nominal width: 400 mm, Width: 995 mm, Height: 850 mm, Depth: 995 mm, Width with packaging: 995 mm, Height with packaging: 850 mm, Depth with packaging: 995 mm, Insertion loss at 125 Hz: 1 dB, Insertion loss at 250 Hz: 9 dB, Insertion loss at 500 Hz: 21 dB, Insertion loss at 1 kHz: 19 dB, insertion loss at 2 kHz: 19 dB, insertion loss at 4 kHz: 16 dB, total insertion loss: 11 dB.