That is something I often rely on ambient noise to do. My work keyboard is quite loud. My home a/c makes a ton of white noise and the occasional thump when it clicks off. It also currently makes a lot of loud water sounds when it is off. I use throat clearing and coughs sometimes, too.

It's a silly game to play with these robocalls what they are/are not listening for and it seems to change from time to time (and obviously from bot to bot). "Dead silence" is sometimes easiest and the easiest way to describe it (though I believe I did mention I generally put things on speaker and rely on ambient noise), but yes, not "required" and it is a dumb space to explore sometimes.