I have the 9-gal Ridgid, and it works well with the nice (HEPA) filter,
but it is definitely loud, and there is not a way to redirect the
exhaust so it's not blowing straight up at you. The "muffler" helps a
little but not much. I'm thinking of building a 1/4" hardboard or
plywood box around it to tame the noise, but for now, I just use
hearing protection. The Ridgid 12-gal model advertises it's 20%
quieter than the 9-gal - I might go with this one if I were doing it
again. The whine really penetrates.
I did quite a bit of looking before I bought this one last year, and as
I understand it, the Ridgid and Craftsman vacs are all made be the same
company now. Shop-vac is the other big brand for consumer-grade vacs,
and they advertise some of their line as "quiet" models, and though I
haven't used one, I've heard (maybe from Amazon.com reviews?) that
they're actually better in terms of noise.
Hope this helps,