I use brown noise from Youtube. There is a 12 hour brown noise video that I play all night, fairly loud. Here's how I am able to listen while I have the screen off on my cell phone. I don't use the youtube app. I use firefox and I go to settings and select desktop site. Then I can turn off my screen and it continues to play (on Android).
I can't find the source just now, but there is something about the ADHD brain having too many thoughts fighting for attention and how adding brown noise is something else fighting for attention and it eventually wins. I started going to sleep faster and staying asleep more once I started.
I wish it wasn't called brown noise though. Sounds like a fart.