ASA 125th Meeting Ottawa 1993 May

5aMU4. Stimulus properties critical to normalization of instrument timbre.

Jennifer L. Cho

Michael D. Hall

Richard E. Pastore

Ctr. for Cognitive and Psycholinguistic Sci., Binghamton Univ., Binghamton, NY 13902-6000

The perceptual system appears to engage in active, time-consuming processes called normalization that maintain perceptual constancy by adjusting for source differences [e.g., Mullennix and Pisoni, J. Acoust. Soc. Am. 85, 365--378 (1989)]. Prior music research [Cho et al., J. Acoust. Soc. Am. 89, 1988(A) (1991)] demonstrated normalization for irrelevant timbre variability in chord identification. The present investigation identified important global components of instrument timbre that may be differentially subject to normalization. Using intact and physically manipulated natural stimuli, experiment 1 used similarity scaling to directly assess contributions of previously identified temporal and spectral properties of timbre. Contributions of attack and upper harmonics were evaluated. Results indicated that similarity was based primarily on the upper harmonics, with little contribution from attack functions. The relevance of these stimulus properties to normalization was evaluated in experiment 2 using an AX chord discrimination task. Normalization, as indicated by RT, was inversely related to similarity. Information present in higher harmonics appears to be the major contributor to instrument timbre and thus is most relevant to normalization. [Research supported by NSF and AFOSR.]