thd

Dear All, I am really sorry if this was already covered, I did not find much info on it. I am quite new to REW. I use Cosmos ADC and SMSL SU-9pro for measurements. (I did use an AP2322 for this purposes till now) I would like to measure THD+N A-weighted and Unweighted as well with sweep...

I've read about a few methods to calculate THD based of IEC or IEEE. Is REW calculating THD relative to the fundamental only or fundamental + harmonics?