The 'ringing' sound people hear isn't actually a sound. It is how the brain processes signals produced by damaged Stereocilia.
If the 'ringing' is constant it means the cilia are permanently damaged. While it would, in theory, be possible to use surgery on the ear and some sort of lazer to completely remove all damaged cilia to avoid them outputting a damaged signal, this procedure would be incredibly invasive and risky. I don't believe it's ever been done and i would find it hard to believe any Otolaryngologist willing to try.