Perceptual and Acoustical Features of Natural and Synthetic Orchestral Instrument Tones

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Abstract
Four experiments were conducted to explore the timbres of natural, continuant orchestral instruments with emulation based on sampling, frequency modulation ( FM) synthesis, and a hybrid consisting of sampling and synthesis techniques combined. Identification of instruments using verbal labels was significantly better for the natural and sampling- based signals than for either FM synthesis or the hybrid technique, a result also found for aural categorization. Perceptual scaling of timbral similarities demonstrated great consistency across a series of independent variables, including musical training, monophonic and stereo presentation, and long versus short signal durations. The first dimension of the classical multidimensional scaling (CMDS) solutions mapped onto long- time- average spectral centroid. The second dimension mapped onto a measure of spectral variability. Little evidence was found for the mapping of attack time or signal duration onto either dimension. A third dimension separated most natural instruments from their emulated counterparts. Experiments using verbal attribute ratings confirmed the correlation of spectral centroid, the first dimension of the perceptual space, and ratings of nasality; the second dimension correlated with spectral variability and modestly correlated with ratings of rich, brilliant, and tremulous. Mismatches of spectral distribution and variability resulted in poor emulations of the natural instruments. Results suggest that further study of centroid and time-variant psychophysical properties is warranted.