Running a PrimaKlima Whisperblower EC/TC with two silencers and added a layer of Aluminum Butyl that's normally used for keeping the vibrations in your car in check.
At ~30% it is super silent. You can only hear a very silent humming noise even if you stand directly next to it.
Held my phone about an inch or two next to it and it measured 40db - that's either pretty nuts or a sign that I have to get a new phone.
I admit: running it at 40% or higher is still a bit noisy without a box, but as it is rn, I only hear some humming and it's not annoying at all.
You could sleep next to that thing without a problem... And I am pretty darn sensitive to noise, since I have tinnitus on both ears.
regards, sh0