New Custom PC Fan 4000 RPM Idle

[dominiclrt]

I recently built a PC and everything seemed fine after I purchased an OS and had everything set up. I started downloading several PC games from Steam and that went fine too. I realized that my fan started making a lot of noise and that was only when I had my browser up. The fan was going 4000RPM at 40C - 45C. Under load it goes up to 5000RPM. I was just curious as to how I could reduce the RPM

Specifications:
CPU - AMD FX-8350
GPU - AMD Radeon HD 7950
MOB - Gigabyte GA-990FXA-UD3
RAM - Corsair 8GB Dual Channel
HDD - Seagate Barracuda 2TB
PSU - Corsair TX750M
Case - Bitfenix Shinobi

 

[getochkn]

What fan? Your CPU fan or case fan? How many case fans do you have? At min, you should have 2. One bringing fresh air, one blowing hot air out. The more, the merrier.

 

[dominiclrt]

The CPU fan I believe, I have 1 case fan at the back and i'm installing a 120mm one in the front