Ordinal scaling of timbre-related spectral audio descriptors

A psychophysical experiment was conducted to perceptually validate several spectral audio features through ordinal scaling: spectral centroid, spectral spread, spectral skewness, odd-to-even harmonic ratio, spectral slope, and harmonic spectral deviation. Several sets of stimuli per audio feature were synthesized at different fundamental frequencies and spectral centroids by controlling (wherever possible) each spectral feature independently of the others, thus isolating the effect that each feature had on the stimulus rankings within each sound set. Listeners were overall able to order stimuli varying along all the spectral features tested when presented with an appropriate spacing of feature values. For specific cases of stimuli in which the ordering task partially failed, psychophysical interpretations are provided to explain listeners' confusions. The results of the ordinal scaling experiment outline trajectories of spectral features that correspond to listeners' perceptions and suggest a number of sound synthesis parameters that could carry timbral contour information.