Well that's not how you measure THD, it's in percentages (such as 0.01%) not dB's, and PC hardware is nowhere near capable of the requirements for decent quality audio measurements.The key question is what is your spec for THD? -60 dB? -80dB? -100 dB?? then how will you verify it? If -60 dB, the solution to both could be a Software Sig Gen. and Spectrum Analyzer. Audacity.exe generate anything you can imagine and detect with AUX input.
Yes of course, but Spectrum Analyzers measure in dB then you convert that to %THD . Last time I used an electret mic with tower Turtle sound card, I was surprised by the SNR and THD it recorded using Audacity. The mic also had a DC response with bias nulled. Let's see how much %THD is -120 dB for the waveform in memory.....Well that's not how you measure THD, it's in percentages (such as 0.01%) not dB's, and PC hardware is nowhere near capable of the requirements for decent quality audio measurements.
I've somehow avoided working with db to this point and recently confronted with a similar ratio question. This THD scenario frames it well.Uhhh ... a dB is a ratio, as is a percentage.
For single-tone audio testing, it is the amplitude of the fundamental. For other situations, there's this:So what's the reference point then?.