Is there any conclusive proof of a treatment to reduce tinnitus?

None, assuming...... Assuming that an acoustic tumor has been ruled out, and assuming that there are no medications causing the tinnitus (aspirin), there is no conclusive treatment.
Get ear evaluation. One of the more common causes of tinnitus is hearing loss, so be sure to have your hearing checked first as a hearing aid may be helpful. Be sure to get checked to see if medications or other medical conditions such as meneire's disease are not the problem. Using a white noise generator can be helpful for some folks too. An herbal remedy called ginkgo biloba has some evidence supporting benefit.