i can hear it through a sheetrock wall over a 14" fan, a 6" and a 4"...
Its 8 trays and when the pumps shut off its like the fucking hoover dam draining in there LOL.
Im moving locations and im thinking about using one huge rez. run a single 1/2" with a T at each tray for the fill tube. A bag ass sump pump so it still fills fairly fast still. Then the drain will be slower as all of them dump through the single 1/2" back to the rez.
and before somebody asks, I use 2x4 trays because they are easy to move and clean and deal with. anything bigger is a fucking pain to even get in a car to take home. and god those 4x8 trays are just monstrous.
I only run my pumps during lights on, which is at night, so its less of a concern for noise, but I do like stealth.