Airborne Noise
While Sound Deadened Steel (SDS) does help with the reduction of airborne noise such as intakes, exhausts and fan blades it is best used in conjunction with noise absorbent foam. While there will be damping of the noise passing through a wall or door which utilises SDS, airborne noise will be reflected back into the room.
The conventional way to deal with airborne noise is to make an enclosure to contain the noise. The enclosure can benefit from including SDS in the construction or by adding self-adhesive dampers after construction, this helps reduce radiated/transmitted noise. The enclosure will also benefit by being lined with SDS AcousticFoam, this absorbs airborne noise and stops it radiating inside the enclosure.
When making an enclosure visualise it full of water... if water can leak out, so can the noise. Sound Dead Steel have close links with many companies that specialise in enclosures/machine guarding and will be delighted to arrange introductions, or manufacture it for you.