Dynamic time warping in percentage
There are no doubt plenty of ways you could define one of the measures in the linked question, but the question remains, after doing so, is the measure in any way meaningful?

This all depends on what you intend to do with the metric after computing it: If it's a perceptual estimate (quality of a Codec,  subjective similarity and so on), you will need a set of measured perceptual data to which you then attempt to fit (mathematically) your measure.