Very nice. I quite like the fan option; don't think I've seen it in other noise generators. The drone of it is good. A 'warehouse fan' option that's a little more bass-y and a little slower would be cool.

For some reason fans / lawnmower type sounds have always been the most relaxing for me, e.g. https://www.youtube.com/watch?v=BcxeZ4Wwdn0 (edit: and now that I post that, a lawnmower sound would be fantastic, but I don't know how much of a weird outlier I am.)