http://www.sounddomain.com/memberpage/522583/7 Using Sony Soundforge 7.0 I synthesized a true 0db 50hz tone and then compared to the "0db" 50hz tone i created via NCH. As you can see it is not 0db and is in fact -12db. I would stay away from NCH for source tones.
Yeah, there was a thread on CAF about this a few months ago. I made some test tones in Matlab. Really easy and works perfectly.