There is SOME audible noise,
however, I can tell you that it can't be anything too straining on the ears.
So long as any electromagentic issues have been addressed (which are rare in most cases),
there is almost no noise coming from it.
I consistently use a SUA3000 here for training purposes and when online,
there is minimal noise anywhere near the unit.
Other than the AVR relays kicking in (which will cause a hum for the duration of the relay being enabled),
the only time the UPS should make any noticeable noise is when on battery or when the fan is on for the aforementioned reasons.