About the calm app:
When you don't think anything (except listening to the soundscape) the volume is low [calm]
When you think a bit the soundscape volume increases [neutral]
When you think a lot the soundscape volume increases A LOT [active]
(When you're calm, you'll hear peaceful weather sounds. When your mind wonders, the weather will intensify, guiding you back to a calm state)
That's how it works, right?
If so my suggestion would be to have an option where if you think absolutely nothing you hear nothing and the volume increases when you start thinking anything. This of course is more advanced level but it would be useful.
OR you could add separate volume controls for calm, normal and active states.
Also what is your favorite soundscape? Mine is ambient sounds.