I don't hear a humming noice from the listening position but if I bring my ear closer to 30 cm, i hear a faint hum both in standby mode or powered.
There is no blower noise and overall, it seems quiet enough for me. (its in a close cabinet)
My cable-internet receiver make more noise.
If I turn off all other equipment in my room, it reads 34dB on a iphone db meter app.
from a 2m distance, it reads. 34-35dB when I turn on the amp so not much difference with my cabinet open.
Directly on the amp, it goes from 34 to 39dB.
Another test from a denon 2313 receiver, I hear a hiss sound from this one. No difference from the listening experience,plus or minus 1dB but creates more noise when i place the meter on top of the amp. It goest from 34dB to 41 in standby and 43 when powered on with nothing connected to it.
So sony seems to have make a better job from these measure.