CPU Heatsink Speed while idle

Hello all. Currently i have a i5 4670k and have a Hyper 212 EVO im going to be installing once i stop being lazy and go buy some isopropyl alcohol to clean off the paste from the stock cooler. In the meantime i want to make the stock cooler not run as loud while idle. Its not really "loud" but its enough to get annoying after a while when there are no other noises occurring in my room. My temps currently are sitting in the 28C-32C area so i feel i have room to work with allowing it to run slightly hotter while idle. My only question is how do i go upon making it run quieter during idle time?

try looking in your motherboard bios, there might be a setting for the cpu fan for silent mode. and if that doesnt work look for the ASUS ai suite drivers for your motherboard, there is a cpu fan setting/control in the fan X-pert program.