It’s in the accessibility settings. You can just search your phone for Background Sounds.

There was an app called Taomix on Android, where you could add sounds on the screen around a marker and the volume of the sounds would vary according to the distance between sound and the marker.

Like you could place a windchime near the marker and birds chirping or a river stream sound a little further away. You could always have new combinations, so that sounds weren't repetitive.

You could then swipe the marker with a push and it would bounce around the screen creating a dynamic sound like passing through a stream or birds singing on your walk.

Then it got bought out by a company and they made a new version with sounds as an in-app purchase, while the previous app was a single purchase.

Then I stopped using it.