I have yet to find a completly quiet bubbler, but most I own become relatively quiet when I use them with barely enough water to cover the perc. Or when you tilt them in a way that has some perc holes almost exposed. Thats how I sneak in those fat hits when we're watching tv or something and I dont want to annoy my people with the constant gurgling noises.
Edit: another way is to use a piece where you can pull the downstem out to clear them. This way it is completly quiet at least when you rip it clear. Milk it nice and slow, with a nice diffused downstem this is not noisy at all, and when you have your hit together, pull the stem for a noisless clear. Applies more to beakers or tubes than your regular bubbler though.