Dynomat is used for vibration muffling not sound.....

Your best bet is really to buy the soundproofing foam, its like 5-15 bucks a square foot and ideally you dont need all that much of it, just enough to muffle the sound, u could use it every other square foot or u could just put it around the walls the fan is near to minimize sound deflection. If you know about sound most of the problem is the deflection and reflection of the waves, so all u need is a little bit but in the right spots good luck.

I had a similar problem all i did was moved the fan from one side of the room to the other