I've done a lot of paxing in both recently, and the Q300 (while a very nice aircraft) is not as quiet as the ATR72-500 (from what I can tell anyway). You just can't beat those six bladed props.
Perhaps the noise on the ramp is all that interior sound being hurled overboard
(although I do think the reference was from inside the aircraft on approach and the ramp, which is outside the scope of the noise reduction system if I'm not mistaken).