Depends what the noise is really.
Some coil whining...
5V standby is always on when PSU is connected to wall and PSU's power switch isn't on off position.
Maybe just little loose wire in coil or mobo drawing power from it at just right space for resonance with that 5Vsb tranformer but hard to know for sure.
With that PSU I would be more worried about long term reliability of its capacitors which tend to be some very cheap ones. (although that problem considers also 5Vsb) You can bet that at that price you don't get Japanese caps and especially when maker is FSP.