BTW One unfortunate feature that many noise apps/websites have (including Apple Music's official noise buttons) is that after a few minutes, they fade out and back in or have some other jarring transition when repeating. This is far from ideal for sleep, meditation, etc. So this is an enhancement request, if your app doesn't already solve this ;)
I'm also curious: do you think that the cost of maintaining the app (keeping it up to date with newer iOS versions, for instance) will eventually dissuade you from keeping it available in its pristine state? I've wondered why there seem to be ZERO free apps by hobbyists on the App Store in categories like this...