The Bose X works quite well in the DHC-8-100/300. I've never been in a -400, so I'm not sure how it would do for any kind of noise in that airplane. As for white noise, I've never noticed a reduction. The headset reduces noise from outside the headset, but static and stuff from the radio isn't really reduced. I think if you buy one you can return it if you decide it doesn't work for the aircraft you're in. I'd also add that I just sent mine back to Bose to do some maintenance on it and am incredibly satisfied. All the stuff I asked them to do was still under warranty and there were no questions asked. I sent it over Christmas and still got it back in about 2 or 3 business days. I haven't had anything but great service from the company. Good luck choosing.