Fan speeding up and slowing down

[HybridSquirrel]

I am listening to my computer now because i dont have my headset on and im not listening to music and it kinda sounds like a fan inside my computer is speeding up and slowing down periodically. i have a dfi lanparty ultra-d and i know it has the speed option in the bios do you think my temps keep coming up and going down? or should i not be worried about it