How to represent ratio between harmonics in audio spectrum I was provided a report where the amplitudes of spectral harmonics have been extracted from several audio files. The amplitudes have been extracted using Audacity's spectrum visualizer, where the spectrum is provided in dB. I want to compute the ratio between the amplitude of the fundamental and the amplitude of each harmonic. Does it make sense to perform a ratio in dB or should I use the difference between amplitudes? Thank you.
I think what you are referring to is called the Total Harmonic Distortion (THD). THD is the level of the fundamental divided by the level of the harmonics.  You can express this as either as a ratio (X/Y), a percentage (X/Y * 100) or in dB (20*log10(X/Y)). A percentage is probably what most people are familiar with.