The effect of amplitude and centroid trajectories on the timbre of percussive and nonpercussive orchestral instruments
John M. Hajda · The Journal of the Acoustical Society of America · 1998
This study explores the salient acoustical attributes of the associative aspects of Western orchestral instrument timbres. Association refers to a subject’s ability to connect or link a stimulus with its intended comparison; this occurs in tasks such as identification, matching, or categorization. Unlike most previous research in instrument association, this study considers both continuant (nonpercussive) and impulse (percussive) classes of instruments. Certain acoustical transformations, such as the partitioning of a signal into attack, steady state, and decay, are not possible for both classes. Findings which have been made regarding the salience of signal segments must be questioned in terms of their application to a more general and inclusive theory of musical timbre. Previous perceptual and timbre synthesis research has demonstrated the importance of global rms amplitude and spectral centroid (the amplitude-weighted mean frequency). Here, both amplitude and centroid are considered in terms of individual trajectories. The evolutions of and relationships between these trajectories are markedly distinct for continuant and impulse classes of instruments. The perceptual significance of these trajectories is measured through the experimental control of their magnitude and direction. A convergence method is employed to ascertain the necessary and sufficient conditions for instrument association.