I've had it for 20 years in both ears, fortunately the same sound and same volume in both, as differing tones/volumes would be worse, imho.
My hearing is perfect, just had a hearing test at Specsavers recently when there for an eyetest. Knowing my hearing is OK is comforting to a degree but it doesn't stop the constant high-pitched buzzing.
The noise increases if I don't get enough, or interrupted sleep and also if I have any other illness. I also think some foods set it off as well, but don't spend enough time tracking this as I try to get on with my life as concentrating on the constant buzzing becomes very annoying.
During the night when everything is much quieter than daytime, it appears worse but it's really just general background noise has decreased. I have a radio and/or music playing 24/7 throughout the house and in the car and find this helps but 'nothing' blocks out 2 x constantly, barking neighbour's dogs...they are horrendous, not only for me, but other neighbours as well. We all yell and scream for them to be quiet, it becomes quite a chorus of human voices at times.
Tinnitus started for me after a virus which left me with several chronic conditions, all untreatable unfortunately. Such is life....