I suddenly got tinnitus a few years ago, and it was after I had started CPAP therapy, for about 6 months or so. I believe there is a causal link between CPAP therapy and tinnitus that is not being reported. Most of the data online points at Sleep Apnea (rather than its therapy) that is the cause, but I find it very suspicious that my Sleep Apnea was being corrected when I got tinnitus for the first time, and I had a machine forcing air into my sinuses every night.
