In my case it was jaw related. I am just over two weeks post op of double jaw surgery (for an overbite). When I woke from the operation, after the initial reaction of feeling groggy, sore and sick, I noticed almost immediately that my tinnitus had gone. I still have a pressure (under water) feeling/sound, but the ''eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee'' ringing is gone. I spoke with my surgeon today and said he's never had that before (in fact he warned me before the op it could make the tinnitus worse) but in my case, it appears to of sorted it..............
I would highly recommend, going to a dentist and having a splint/mouth guard made up (think it cost £30 last time I did it). Not been able to use mine for years because of the braces (just not practical) but when I did have it, I noticed a dramatic reduction in my tinnitus after a few months of use. At worse it stopped me grinding my teeth.