Signal-Dependent Nonlinearities for Physical Models Using Time-Varying Fractional Delay Filters

Vesa Välimäki, Tero Tolonen, and Matti Karjalainen

Helsinki University of Technology, Laboratory of Acoustics and Audio Signal Processing, P.O. Box 3000, FIN-02015 HUT, Espoo, Finland

ABSTRACT

This paper discusses the use of nonlinear filters that are based on linear digital filters with input-signal-dependent coefficients in the context of digital waveguide synthesis models. It is proposed that the practical uses of such filters in music synthesis may be generalized to a time-varying fractional delay (TVFD) filter with signal-dependent coefficients. Three different cases are outlined: 1) simulation of a pressure-dependent wave propagation speed in a wind instrument bore, 2) nonlinear termination of a vibrating string, and 3) a tension-dependent variable speed of transverse vibrations on a string. Implementation structures for TVFD filters based on FIR filters are suggested.

Keywords: audio signal processing, physical modeling of musical instruments, sound synthesis, interpolation, musical acoustics, vibrating string

This paper was published in the Proceedings of the 1998 International Computer Music Conference, pp. 264-267, Ann Arbor, Michigan, USA, Oct. 1-6, 1998.

• The complete paper in PostScript format (323 kB)
• The complete paper in PDF format (40 kB)
• The ICMC98 presentation slides in PDF format (73 kB)
• Sound examples played at the ICMC98 presentation
  1. Output of a linear string model: linstr.wav
  2. Output of a nonlinear string model using a first-order allpass filter: ap1str.wav
  3. Output of a nonlinear string model using a first-order Lagrange interpolator: lagr1str.wav
  4. Output of a nonlinear string model using a second-order Lagrange interpolator: lagr2str.wav

This URL: http://www.acoustics.hut.fi/~vpv/publications/icmc98.htm
Last modified: December 1, 1998
Author: Vesa Välimäki