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  • Research Article
  • Open Access

Multirate Simulations of String Vibrations Including Nonlinear Fret-String Interactions Using the Functional Transformation Method

EURASIP Journal on Advances in Signal Processing20042004:745924

  • Received: 30 June 2003
  • Published:


The functional transformation method (FTM) is a well-established mathematical method for accurate simulations of multidimensional physical systems from various fields of science, including optics, heat and mass transfer, electrical engineering, and acoustics. This paper applies the FTM to real-time simulations of transversal vibrating strings. First, a physical model of a transversal vibrating lossy and dispersive string is derived. Afterwards, this model is solved with the FTM for two cases: the ideally linearly vibrating string and the string interacting nonlinearly with the frets. It is shown that accurate and stable simulations can be achieved with the discretization of the continuous solution at audio rate. Both simulations can also be performed with a multirate approach with only minor degradations of the simulation accuracy but with preservation of stability. This saves almost 80% of the computational cost for the simulation of a six-string guitar and therefore it is in the range of the computational cost for digital waveguide simulations.

Keywords and phrases

  • multidimensional system
  • vibrating string
  • partial differential equation
  • functional transformation
  • nonlinear
  • multirate approach

Authors’ Affiliations

Multimedia Communications and Signal Processing, University of Erlangen-Nuremberg, Cauerstrasse 7, Erlangen, 91058, Germany
Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, P.O. Box 3000, Espoo, 02015, Finland


© Trautmann and Rabenstein 2004