Using an SPL meter app called SPL Meter of all things with a relative function to zero out background noise like my AC. My CTC puts out an average of 15Db at 1 foot away. At 10 feet it is about 5Db. So yes there are some very quite printers out there if you tune them correctly.
You want to set vref on all motors so it is just enough to move them with out binding and no more. This also helps them run cooler which will let them last longer as well.
Printing since 2009 and still love it!
Anycubic 4MAX best $225 ever invested.
Voxelabs Proxima SLA. 6 inch 2k Mono LCD.
Anycubic Predator, massive Delta machine. 450 x 370 print envelope.