We bought a fan a couple years back, they were all rated for noise level in Sones...whatver they are, but the smaller the number, the quieter they were.
My tip: Do not oversize the fan for your bathroom size - I got a bigger one than recommended and it's a cool breeze in the shower stall....
Never ascribe to Evil that which is more resonably explained by Ignorance and Stupidity
There's casting, then there's running into the stream with a baseball bat trying to club the fish to death. - Jim Moore