I have ultra high pitched ringing like dog-whistle in both ears. It is so unearthly I haven't found anything in my experience with that kind of sound. If you take the dentist drill and multiply it 20 times in pitch, it may hit that range. Plus it is such a condense, piercing sound, like a lazer shooting up the dark sky. The right ear is worse than the left but they were both unbearable, at least at the start, to this anxiety & panic prone mind. I never thought human can tolerate such sound 7/24. That is why I had relentless anxiety and panic attacks on auto mode daily & hourly and I had to depend on meds to survive each long dark day. Nowadays, the brain gets used to the same repeated stimulus. I don't know how it does it. But it may be like my experience in learning to eat spicy hot foods. In the beginning my brain rejected the spicy sensation. It gave me quite an unpleasant sensation even with a small bite of a mild pepper and I had to use cold water to put off the 'fire'. But because I didn't consider this a threat to my survival and kept at it. Now heck I can chew a raw chili and and didn't feel it much, and surprisingly the brain now considers the 'fire' of spiciness a pleasant sensation. Go figure. So I guess in similar way, the brain has re-wired itself to accept that the ultra high pitched T sensation is tolerable and livable. It no longer dangles out the big 'S' word in front of me due to this ridiculously high pitched sound like it did during the worst time. LOL.
As far a a high and a low humming tone, after all these years of reading forum posts, I feel it is quite common, as illustrated by many posters here. I still remember the funny experience of watching that youtube clip of David Letterman who has the same high & low tone ringing. He was doing his comedian show with another T sufferer, Captain Kirk (William Shatner) in 1996 and both of them talked about their T condition. Letterman was joking that his high & low tone T is like the emergency broadcast system on test mode non-stop 7/24, even when he was trying to entertaining his audience. So has some sympathy, he said jokingly. He said back then his T was getting worse, but as of today he is still cracking jokes and remain productive and entertaining. So his worsening T obviously hasn't stopped him from living a normal & productive, especially entertaining life. LOL. I had a blast watching this video and it helps be back then to feel not so desperate about my T. Hope you can have a smile watching this video: