For my ADHD iPhone users and others who need white noise:
iOS 15 and iPad OS 15 has a feature in the accessibility menu called background sounds (settings>accessibility>audio/visual>background sounds) where it will play the selected sound in the background across the entire OS. You can have it play in the background of media as well and also with the phone locked. I know third party apps exist but I know Calm on iOS doesn’t have the ability to control the volume on soundscapes without affecting the system volume.
If you have an iPhone 8 or later running iOS 14 or 15, you can enable Back Tap (settings>accessibility>touch>back tap) and set Background Sounds (or any other option) to a double or triple tap on the back of the iPhone.










