A customer wanted the quietest 3kva UPS. After checking APC's SUA3000, Eaton's Online PW9130, Liebert's PSI3, and Tripplite's SU3000 units, I found all of them had Audible Noise at 1 meter of 53-55db.
I then checked premium APC models, Rack versions, etc and couldnt find anything quieter. Finally, I found the SMT3000 5th Gen APC unit that had only 45db rating.
I guess all makers use the same basic components and have no motivation to distinguish themselves on db level.
