The plot can be made more psychologically real by changing the frequency scale to the Bark scale, and using an auditory filter to smear the spectrum. The distance between two spectra represented in ways similar to this can be calculated as a Euclidean distance, and compared with psychoacoustic data. Here, we are comparing two time-varying spectra which are very similar to one another. This would be used to measure the efficiency of a particular synthesis technique. Spectral pitches correspond to individual audible pure-tone components.
Most pitches perceived in everyday and musical sounds are virtual pitches.
The relative perceptual salience of pitches may be estimated by the algorithm of Terhardt et al. Metrics have a long tradition in the literature, beginning with Fechner in the 19th Century. Cognitive science, however, points out that perceptual space may be non-Euclidean. In other words, there is NO simple metric. Algorithm for extraction of pitch and pitch salience from complex tonal signals.