Its called pulsitile tinnitus

The sound you are hearing is most likely from a blood vessel that is adjacent to the ear structure. It is often related to position and usually of short duration. If it persists or is constant I would want it checked out.

Tinnitus is often caused by hearing loss. It can also be a side effect of medications or related to anatomical problems.

Well, could be a number of things. Is it constant, intermittent, recurring, or temporary? The term for noises in the ears is tinnitus. The most common cause is noise exposure, but there are many other causes (i.e., change in blood flow to inner ear, wax buildup, hearing loss, high blood alcohol level, head trauma, medications, bacterial/viral infection, etc). Are you also noticing a change in hearing? First step could be to see an audiologist to have your hearing evaluated.