Much louder than the cherry mx blue. There's a spring inside which buckles sideways. The point at which it buckles provides the physical and audio feedback.
Which is the big difference to all the Cherry switches: Those are inherently linear (and quiet), some variants just have plastic latches glued to a side to emulate the clicking noise and tactile feedback (both of which useless, because they're decoupled from actual actuation).
A typewriter. Not quite as loud as a mechanical typewriter, but slightly louder than an electronic typewriter and, since you don't have to wait for the keys to come back, there is practically no limit on how fast you can type.