How can I get audio apps (music, podcasts, Audible audiobooks) to automatically pause when another app (alerts, Maps directions) interrupts?

I know in some previous iOS it did this but somewhere along the line it got lost. I listen to podcasts and audiobooks a lot and when another app speaks or makes a sound, the volume on whatever I'm listening to goes way down until the interruption is done. If it's a book or a podcast I've missed something and have to go back, which is annoying at best, and dangerous, at worst, when I'm driving.