If you're looking for soundproofing guides, here's two guides that I have saved on my browser.
This guide by philipma1957 is more oriented towards BTC miners like the S9 and S7, but it should also work for the D3. Fire resistant, fits 2 Antminer-sized units and works very well.
This enclosure also seems to be somewhat fireproof and should work decently, but it only fits one unit. Cost for this is around $120.
If you decide to purchase something for soundproofing, don't go for something like
this. This type of noise reducer hardly does anything and you're better off with the two solutions I linked above.