A few years ago, I had an iOS app that did audio notch therapy for tinnitus. Does the therapy actually work? For some people, maybe. From what I remember, the research papers I read on the subject indicated the therapy can help. I conducted a small study with the audiology dept at a local university, but I didn't reach any useful conclusion. In the end, I suspect notch therapy ends up working similarly to masking therapy (using white noise or other sound to cover up the tinnitus).