Sound Source Identification: The Possible Role of Timbre Transformations

Timbre is typically investigated as a perceptual attribute that differentiates instruments at one pitch. Yet the perceptual usefulness of timbre is that it allows listeners to recognize one instrument at different pitches. Using stimuli produced across the playing range by three wind instruments from two categories, woodwind and brass, we measured listeners' judgments of instrumental timbre across pitch in a dissimilarity task and measured listeners' ability to identify stimuli as being produced by the same or different instrument in a three-note oddball task. The resulting multidimensional scaling representation showed that Dimension 1 correlated with pitch, whereas Dimension 2 correlated with spectral centroid and separated the instrumental stimuli into the categories woodwind and brass. For three-note sequences, the task was extremely difficult for the woodwind pair, with listeners typically choosing the most dissimilarly pitched stimulus as coming from the oddball source. In contrast, the three-note sequences were easy for the woodwind-brass pairs. The results from these experiments illustrate the difficulty of extrapolating the timbre of a sound source across large differences in pitch.