Case fan speed controller

Yes. You can switch the speed of your fans via your BIOS, use a program like Speedfan (easier) or use a piece of hardware that u can install in front or back of the case with little knobs.
Either way, u can control the speed of them. Turning them off is probably not recommended, it can overheat the cpu pretty fast if the fans are not enough or not spinning fast enough.
You can find multiple video tutorials on how to do it, just google it and you'll find easy answers :)
 
Maybe something like this.

http://www.xoxide.com/sunbeam-rheosmart-6-fan-controller.html

Or one of these
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&DEPA=0&Order=BESTMATCH&Description=nzxt+sentry+2&N=-1&isNodeId=1

I've got an older sunbeam 4 channel controller, it's rheobus type with knobs. Some fan controllers are a bit poor quality, I didn't expect much from the sunbeam but honestly it's been a nice controller and lasted through several builds. The knobs have smooth operation for fine control. A lot better control over fan speed/noise than the bios gives. Some people swear by speedfan but I've never gotten it to fully recognize all my fans. If it works for others, great but personally it's not worth the space it takes up on my hard drive.