Hey Sean, I don't suffer from tinnitus, but I use something that is designed for it. I am an extremely light sleeper, and as a result I have had to invest in a tiny sound machine that was also designed for folks with your condition. It allows me to sleep in my tent near a noisy fire when I am on adventure travel. Here is the website: https://www.soundoasis.com/products/sleep-sound-therapy-systems/worlds-smallest-white-noise-machine/

Kindly I make no assumptions that this will help; all I know is that it was designed for tinnitus, and it might be valuable if you haven't looked into this already. Luck of the draw, we never know what we're going to get, only that we will get curve balls.

There is a significant discount on these for vets, so your dad could secure a bunch for you if you want a deal. I use the tiny oval one; it is so light you barely even register its existence. For me this has been a lifesaver on noisy international trips and adventures. Best of luck, Sean.