which frequencies are used in multi tone measurements?

[LTig]

Hi,

here in ASR I saw the first time multi tone THD measurements. I really like this type of THD measurement because it shows a lot of information in one single spectrum.

However I could not find information about how the frequencies of the different sinus tones are calculated. It's clear that they must be chosen such that higher frequencies are not multiples of lower frequencies so the distortion products of the lower tones are not masked by the higher tones. Can someone point me to a paper or a link where such a formular is explained?

Thanks a lot.

 

[MZKM]

https://www.ap.com/technical-library/using-multitones-in-audio-test/

 

[RayDunzl]

Can someone point me to a paper or a link where such a formular is explained?

The tones with the phase of the tones used here:

https://www.audiosciencereview.com/...-of-schiit-audio-dacs.5487/page-3#post-121956