If you do implement a voice/breathing etc. Then it would probably be a decent idea to control it with a separate audio slider in the settings, that way people can just 'fix' whatever issue they have instead of anything being a deal-breaker.
That's exactly what I would do. I already have a "Player" volume slider, with a heartbeat specific slider as a child of the player section. I would just make "voice" another child of the master "player" audio.
