My tinnitus started almost a year ago, and it bothers me throughout the day. Fortunately, I haven't noticed a change in the sibilance level from my audio systems. Does this rule out tinnitus as the cause? I don't know, but I want to emphasize that there might be a correlation rather than a causation.
I recall two instances where I observed improvements in the sibilance level. The first occurred during an audition of the Wharfedale Evo4.2 speakers, where the sibilance level diminished substantially to my surprise. However, I opted to return them due to other considerations. The second instance was when I introduced a preamp into my system’s chain. It notably enhanced sound quality in almost every aspect, including sibilance control. In my case, it appears to be gear-dependent.