It's tough to diagnose sounds without being there but is is a soft "wirr" or a grinding sound. If it's just a soft whoosh, chains aren't dead silent and maybe just additional chain lube will quiet it down.
If it is unusually noisy, your chainline may be a bit off. Place a straight edge along the chainring and see if it passes directly over the rear cog. If the two aren't line up nearly exactly, add spacers to one ot the other to correct the misalignment. Also, is the chain tension right? Too loose or too tight could be the problem.