Dimensional tradeoffs in the perception of complex tone sequences

Abstract

Rapidly occurring sequences comprising sounds that differ along some dimension can often be perceptually grouped into subsequences or “streams.” A study demonstrating the use of differences in timbre to provide a basis for stream segregation used four‐tone sequences of the type: TxPx TyPx TxPy TyPy, where T and P refer to the timbre and pitch attributes of the complex tones. Forty‐nine such sequences were constructed, with the first pair of tones having same pitch Px, but different timbres, and the second pair having pitch Py, and similarly differing timbres. The absolute position of the spectrum was varied to provide timbral “distances” between sounds, and relative spacing between harmonics varied to provide differences in pitch. Six listeners indicated their perceived grouping of the patterns, as being based on pitch, on timbral segregation, or ambiguous groupings not dominated by either cue. Results indicate that differences in spectra affecting either the timbre of the tones, or the pitch, or both, lead to tradeoffs between these attributes in determining the grouped percept and imply that the stream segregation phenomenon may therefore be based on spectral proximity of the sequential tones. [Work supported by NINCDS.]