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Rapid Approximation of Weakly-Nonlinear Mode Parameters

Modal processors and synthesizers require determining resonant frequencies and decay rates of a system. We introduce a simple, efficient, and flexible approach to compute these parameters when speed is of the essence, for example modeling a user’s sample folder in a realtime mobile synthesizer application. The approach compares DFT peaks in two impulse response windows at different points in time to obtain the modal frequencies and decay rates. The approach trades precision for speed, and should be considered an approximation. For a selection of samples across tonal/atonal instruments and reverb responses, we consider sensitivity to window choice and window size, and compare results to traditional modeling methods, which operate on the entire impulse response. We propose extensions of the algorithm to more than two windows, and to capture nonlinear, time-varying behavior such as the pitch dive after striking a tom drum at high velocity.

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AES - Audio Engineering Society