that is typical. there can be hundreds of causes of tinnitus (ringing) and it is actually rare that a specific cause is found. i know. i have had tinnitus myself for well over a decade. all of my tests were blind alleys like i expected. the ent is really obligated to search for a cause (like an acoustic neuroma) but these are rarely found. most of the time the ent just throws in the towel and essentially tells you to just "live with it". and so we must. there are treatments that help you cope with tinnitus but it is unlikely that you will find a miraculous cure. it can just go away (which is nice) but it has a good chance of staying with you for a long long time. i wish i had better new for you but tinnitus is perhaps one of the most difficult medical problems to investigate and one of the most difficult to treat.
i have constanct ringing in my ears doctors cannot find anything wrong even with mri's. any suggestions?