Itís possible to order the fans with a soundproof cover "at sight."

The soundproofing consists of applying on the case a high noise absorption cover; this expedient allows to low the average noise up to 10 db(A) (according to the type of fan) and it  results cheaper than other methods (i.e. soundproofed boxes).

Additionally it is also convenient to climb on a silencer on the fan outlet or fan inlet that allows a further average lowering from 3 to 8 db(A).  

The pictures show the VC HL 50 with silencer on the fan outlet and butterfly regulation shutter on the fan inlet.