>holding both volume keys turns talkback on and off, and android plays a sound when you do it. a very loud sound. WHY IS IT SO LOUD

The fun part about it is that even if you lower TalkBack's sound, enable the debug tool that just writes the text in a toast because listening to accessibility announcements all day long is a recipe to go mad, turning it on/off always give you the horribly loud TALKBACK ENABLED, all my colleagues know when one of us is doing accessibility work.