I had tinnitus really bad when I was exposed to a loud sound where I lived, 24/7, similar to Sarah's Sister's situation, where there was a frequency. I clenched my jaw constantly - already had TMJ, but it got much worse. I think that's what caused my tinnitus. Well, it sounded like spaceships had landed!
I took a lot of magnesium, and it helped a lot, to relax my jaw, and magnesium is good for the ears, too.