I've had tinnitus for several months now and it's extremely annoying and makes it difficult to think about anything else. It's similar to this except mine has a slightly higher pitch. My neurologist brushed it off and said there are hundreds of causes for tinnutus. I'm inclined to believe that it's related to low blood flow to the inner ear. This theory comes from the fact that my POTS became much more severe, my heart started struggling to beat normally even at rest, frequent chest pain... at the same time my tinnutus started. Any one else see a correlation between heart function, POTS and their tinnitus? Google found several papers describing using tinnitus as a predictor for heart problems (non-CFS related papers).