Get yourself a Huma Mod 40 if you want really quiet.
I’m basing this on the Huma Mod 30s and 40s (I own several) with the felt inserts. I have not tried the latest Humas with the baffle inserts (Avalanche)
Trenier sells the Avalanche Mod 40 and 30:
These airgun use only moderators have a unique, lightweight and modular system (Patent Pending) allowing you to configure your personal airgun moderator in terms of length. The MOD40-4/0 series moderator includes the base module (chamber) with a 1/2″-20 UNF thread, two center 40mm center chamber...
www.trenierairguns.com
If you want super quiet, you can replace the felt with rolled cork (cheap 1/4” cork sheets off Amazon) in one of the sections. Humas are modular so you can use as few sections as you need:
Hygloss Cork Roll 1.5 mm Thick-12" x 24"-Brown-1 Qty
https://a.co/d/dGiebxV The Huma design is basically a copy of the legendary Weihrauch 30mm tube design. It works great and is ADJUSTABLE… you can add felt layers, remove felt, use cork, add more sections internally, etc.
I‘ve got multiple Donny moderators. They look nice and do a reasonable job for their size, but they are not your 1st choice for quietness in my experience. They are also completely unadjustable with that monocore design. You can’t even add an additional layer of felt.
I’ve also made lots of moderators. If you have a low power gun, a Buck Rail 3d printed mod will be pretty quiet. If its a higher power airgun (40+ ft/lbs) try a Huma.
BTW, I’ve got a Huma Mod40 on my 30 cal Prophet shooting 72ft/lbs and its backyard friendly. I couldn’t believe it - thought the .30 would be to loud in the yard.
-Ed