Does this sound happen when you are breathing? Or does it occur all the time?
It might be Tinnitus? Tinnitus can come in many different forms from clicking to ringing to roaring sounds...look it up online.

If it only happens when you breathe you might have a condition called Patulous Eustachian Tube where the tube connecting your nose to you middle ear stays open when it's supposed to be closed, allowing internal sounds like your breath to travel up the tube and vibrate youe ear drum.

Do you have any other ear/head symptoms?

Good luck!