Does Timbral Brightness Scale with Frequency and Spectral Centroid?

Two models that predict perceived timbral brightness in terms of the centroid of the frequency spectrum were investigated. One model simply uses the centroid of the frequency spectrum, the other divides this same value by the fundamental frequency: the latter scales the centroid of the frequency spectrum with the fundamental frequency. Different single tone and pitch combinations, presented sequentially, were compared. Participants were not asked to ignore pitch differences and intervals of greater than an octave were compared. The results indicate that brightness is much better correlated with frequency spectrum centroid (r = 0.513, p < 0.01) than with the ratio of the centroid of the frequency spectrum to the fundamental frequency (r = 0.030, p = 0.441).