This isn't a question, I just wanted to give any other new Muse users this tip, because I didn't see a lot of discussion regarding feedback when I was still troubleshooting this issue.
During my sessions I found that the background noise was too similar to the feedback noise, a separate issue on it's own, but I mention it to explain that I'm using the Muse with the background volume muted out, with only the feedback remaining. however, I've found the feedback is still too loud, even when I am trying to concentrate. I understand that my level of deliberate concentration may not be very strong, so to fix this, I've turned the volume down on that as well to a bare minimum, so that even a shallow increase in concentration will produce silence.
Thank you for reading, and good luck