Nudges.
And that's the problem. They never state how loud verbal components are, and when directly asked, have always evaded the question and left it up to DMs. So we're in this bizarre state where verbal components might be something you can whisper, or might be something you have to yell at the top of your voice, depending entirely on your DM and how they are feeling today.
I agree broadly that there is some suggestion that verbal components are non-silent but that's as far as it goes. And a lot of the suggestion is merely implied by the existence of Silence and Sorcerer metamagic.