Stochastic Excitation for Quasi-Periodic Synthesis

For good generality, at least one of the excitation signals should be a filtered noise signal [440]. An example implementation is shown in Fig. 9.57, in which there is a free-running bandlimited noise generator filtered by a finite impulse response (FIR) digital filter. As noted in §9.4.4, such a filtered-noise signal can synthesize the perceptual equivalent of the impulse response of many high-frequency modes that have been separated from the lower frequency modes in commuted synthesis (§8.7.1). It can also handle pluck models in which successive plucking variations are imposed by the FIR filter coefficients.

In a simple implementation, only two gains might be used, allowing simple interpolation from one filter to the next, and providing an overall amplitude control for the noise component of the excitation signal.

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About the Author: Julius Orion Smith III
Julius Smith's background is in electrical engineering (BS Rice 1975, PhD Stanford 1983). He is presently Professor of Music and Associate Professor (by courtesy) of Electrical Engineering at Stanford's Center for Computer Research in Music and Acoustics (CCRMA), teaching courses and pursuing research related to signal processing applied to music and audio systems. See http://ccrma.stanford.edu/~jos/ for details.