Hello,
I my hiss is very high pitch too. I'm not sure, but it seems to be around 15000 hz.
I found out that using
https://mynoise.net/NoiseMachines/ultrasonicNoiseGenerator.php Starry night preset allows me to mask it completely. If I'm feeling very stressed I use this noise generator and turn up the volume just so that I can hear the hissing on the same level. I found out that after listening for 1-2 hours of this I can cope much better, but it's still tough.
I find coping with this high pitch hiss very hard, because the sound is so unnatural. Even if it's relatively loud around me I can still hear it breaking through and it causes a lot of distress.
I have a tone like a Morse code and some trembling and pressure in my left ear and I have habituated to it fully within 1.5 months since this whole thing started, but I can't get used to the hiss even though it's just a bit louder than the tones. I think my hiss is about 60 db. I can hear it in 65 db environments.
Sometimes I feel like the left side of my head is on fire, because of this hiss. I suspect I might have TTTS.
By the way, I've seen your posts when I was researching this forum. Do you think your tinnitus has been caused by ETD? My doctors suspect this, because have negative pressure on my tympanometry. I'm going to another doctor today.
And looking at your profile I see this post "When my ears feel full my tinnitus is not as loud as when my ears feel more open..."
Yes, I feel exactly the same! I have these episodes when my left ear feels somewhat full and throbbing. Like something is physically moving my eardrum and pushing on it. Sometimes it's synced with my pulse. During this episode the hissing diminished greatly to the point it's almost nonexistent.