The noise cancelling (NVS) works up to a point. The first time I flew on the aircraft on a familiarisation flight before I did my training on it, I said to the cabin crew "I thought the Q400 was suppsoed to be quiet, is the NVS switched on...?" "oh yes" she said "let me show you what it's like with with it switched off..." The noise levels with it switched off are enough to make your ears bleed (almost). So it does work.
Having said that, compared to the other turboprop which I flew as well (328). The Q400 was noisier inside with the NVS switched on than the 328 which has no NVS at all. Also flew on an ATR 42-500 (as a passenger) recently and it was quieter then the Q400 as well. The Dash 8-300 is noisier though. (Don't know about the Q300 though as have never been in one).
The Q400 also has quite high noise levels in the flightdeck as the wipers create quite a lot of airflow noise aound them, and they sometimes make a strange whistling noise when flying through cloud.
Good luck with your uni course, if you need any photos of any bits of the aircraft let me know and I can email them.