So far.. nearly all fan companies give good readings about how loud their fans are. What you're missing though, is that a fan company will tell you how loud the fan is when it's just sitting on a table or something. Once you put a fan up to a case wall, or have it screwed into your window etc.. sound levels change drastically.
I would suggest getting some rubber mounts instead of using screws. I've used them in my build where I have nine 65+CFM fans, and honestly it's pretty quiet (for a full size, gaming machine).
You can get them here:http://www.quietpc.com/gb-en-gbp/products/casefanaccessories/afm02b-group
Luckily I have a trade account with QuietPC so I can buy hundreds of these for cheap.. but even paying full price - trust me they make a difference!
Most of the sound a fan makes is actually it vibrating the case around it because you've screwed it in tight. If I touch the top of my case I can hardly feel anything at all, and that's with 12 fans in there all together at 100%.. compared to my dads machine that has 2 fans in it and vibrates like a toy joy rabbit