The ringing sensation that can be detected in your head or individual ears is called tinnitus. Usually, this ringing is an indication of damage to your auditory system, especially noise damage. The ringing can be constant or periodic, and can occur in the middle of your head or on a specific side.
Sometimes, hearing instruments help by bringing more sound to the brain, helping distract attention from the ringing. If you experience constant ringing on one side, it is ideal that you ask your doctor about it.