conway filter posted above, you can't really hear it from 10ft when it runs on low speed (it has sensor and he autoadjusts ).
i also have iqair which according to reviews is quiet at low speed. in my experience this quiet sounds like airplane (i got it replaced once. apparently it's just the way it is).
I think you're missing his point entirely. The problem with these retail purifiers is that you either get quiet or effective. You don't get both.
Sure, you can't hear it from 10ft away - but how much air is it moving at that setting?
I have various configurations of these PC fan setups and the Arctic P14 Pro that you can get 5 for $32 on amazon are honestly wildly effective and designed for applications with some static pressure (radiators and such).
So we're back to; effective or quiet, you're only going to get both with the PC fans, for now.
i also have iqair which according to reviews is quiet at low speed. in my experience this quiet sounds like airplane (i got it replaced once. apparently it's just the way it is).