After a few weeks of using the app for 10-15 minutes/day, I’m afraid that I don’t have much progress to report. I haven’t noticed any change in my tinnitus at all. This could be due to incorrect usage of the app and/or to my not being 100% sure of the correct frequency of the ringing in my ears, something that apparently is fundamental for this therapy to be effective at all.
Also, according to various sources I’ve looked at, ACRN therapy is supposed to be used for several hours a day, something I’m not exactly sure how to implement. Wearing AirPods several hours per day is not practical, at least not for me. So I’m currently considering re-starting therapy, this time perhaps AirPlaying the tones to my HomePod (wearing headphones is recommended but there appears to be evidence that “ambient” tones can also help). Another option is to dust off my EarPods (the wired headset that came with older iPhones) and see if I can hit 60 minutes per day to start with, without worrying about headset battery drain.
Edit: If you’d like to try this without spending the 7 bucks, here’s a resource that may interest you:
Lastly, have a look through this (long) thread to see others’ experiences with ACRN (including posts from someone who was actually in one of the clinical trials):