Virtually silent. The ones I have don’t even click while free-wheeling.

I actually view this as a downside, or at best neutral. I find the click of free-wheeling to be the most effective way to alert pedestrians to your presence, because a bell should not be used except as an equivalent to a car horn (and pedestrians often react unpredictably if you misuse it), and your voice can sometimes come across as a little aggressive even if the intent was purely informational. But the click of a freehub makes it clear you're there, while also making it clear that you're slowing down and being patient/careful.