A Finite Difference Method for the Excitation of a Digital Waveguide String Model

With Digital Waveguide modeling (DWG) a number of excitation methods have been proposed to feed the delay line properly. Generally speaking these may be based on signal models fitting recorded samples, excitation signals extracted from recorded samples or digital filter networks. While allowing for a stable, computationally efficient sound emulation, they may be unable to emulate secondary effects generated by the physical interaction of, e.g., distributed interaction of string and hammer. On the other hand, FDTD (Finite Difference Time Domain) models are more accurate in the emulation of the physical excitation mechanism at the expense of a higher computational cost and a complex coefficient design to ensure numerical stability. In this work a mixed model is proposed composed of a second-order FDTD model, a commuted DWG and an adaptor block to join the two sections. Properties of the model are provided and computer results are given for the case of the Clavinet tangent-string mechanism as an example application.