I JUST bought a new fan to replace the one in our upstairs bathroom. The one that is there is undersized and noisy. Havent installed it yet though.
I got it at Menards. They have a nice display where you can turn on the fans and see how noisy/quiet they are. All I remember is that the one I got is a Broan and its 100 or 120 cfm.
I wouldn't vent it up to your ridge vent. I think you should go through the roof or a side wall with a weather cap that has a closing flap. You DO NOT want warm, moist air going into your attic space.
Also, if you use the plastic accordion style vent tubing, how much you stretch it out will affect how much noise the fan makes. You do want to stretch it out somewhat.
Another thing I've done is to put in a timer switch for the fan. That way after doing whatever in the bathroom, you can hit 10, 20, 30 or 60 minutes on the timer and forget about it. That way you don't accidentally leave the fan on all day.l
Dave in WI
"Daddy, it's five o'clock sometime!"