The use case is e.g. when I want to turn on breathing activity during a lecture. But I don't want to alarm anyone with the ending sounds, starting sounds and star-end activity sounds. It's just inappropriate. I know Do not disturb disallows incoming notifications to make sounds, but that's not quite what I'm looking for. I would like to set an activity not to make sounds, or to just turn off all sounds for some period and then I'd turn them back on again.
