Sure https://www.youtube.com/watch?v=kO2yFC7_k2s
I should have posted it to begin with, sorry.
Ideally, an amplifier should give a linear relationship between power_in and power_out. A linear relationship means that if power_in is doubled, then power_out is doubled, and if power_in is 4x, then power_out is 4x, and so on.
At higher power, the linear relationship deteriorates, but the problem is that the out/in curve grows less than the linear relationship, which means that you can't get quadruple power_out out of a doubling of power_in. See https://en.wikipedia.org/wiki/Gain_compression.
Based on these points, I don't think you can say the audio has to do with amplification (although if anyone disagrees, please let me know). As far as I know, for any wave, the intensity is related to the square of the amplitude. This means that the amplitude doubles in constructive interference, but the energy has to quadruple (and that energy should come from the destructive interference).