My HHKB Hybrid Type-S is definitely less noisy than MX-Brown (at least in WASD keyboards edition).
It may be more silent than my typing on macbook air, but it's hard to compare because it produces lower frequencies, definitely nicer sound than macbook keyboard to me and never even thought about it as noisy.
That's the exact HHKB I have and trust me, it's a noisy rattly mess compared to a good mech.
Like just lightly glide your fingers across the keys and you should feel/hear the rattle. That same rattle continues as you type, it's just mixed in with the sound of bottoming out.
For comparison, my mech is a solid feeling piece of aluminum, the keys have 0 wobble, and there are no rattles at all.
It's night and day, I could never go back to a HHKB.
I currently use an HHKB (for almost 10 years now) and I love it. But RSI has pushed me towards building my own split ergonomic ortho keyboard. What switches are you currently using on your daily driver mech? I got some 67g Zilents that I'm hoping give me a fairly close feel to my Topres when lubricated.
Having used every tactile from Zilents to Holy Pandas, these are the first switches I'd consider a strict upgrade over the competition (including Topres)
They're crisp, come in silent and unsilenced (I prefer silent), and have uncanny tolerances which results in a consistency Topres can't match.
I also have a type-s hhkb with the silencing o-rings and I’ve never thought that it sounds noisy.
I’ve experimented with various keyboards but for me the sound and the action of the hhkb are my favorite. I just wish it had the layout of the Leopold FC660C.
I examined mine carefully after reading your comments and.. did you buy it directly from HHKB? Maybe you have some counterfeit?
But you may be right, I'm not such a keyboard aficionado, I only had a few mechanical keyboards and maybe my standards are too low (or rather, at level which keeps me happy).
But as somebody else noted if you found the holy grail please share.
It may be more silent than my typing on macbook air, but it's hard to compare because it produces lower frequencies, definitely nicer sound than macbook keyboard to me and never even thought about it as noisy.