How do you turn down PC fans?

As I go on skype with friends everyday, they complain of how there is a ton of background noise, no its not the tv or anything else, its dead silent exept for my PC. As i go into task manger, it says that im only using 4%cpu, 38%Memory, and 0 disk and network, and my pc is loud. I tried looking at youtube videos of how to make it quieter, but its always WD40 or other crap that I don't think works. I have win. 10 if that helps, along with GTX 970 :P thx