Waveguide synthesis models acoustic resonators as digital delay lines with filters, efficiently simulating instrument resonances

Digital waveguide synthesis (Julius O. Smith, 1983) models acoustic instrument resonators: strings, bores, membranes: as delay lines representing the travel of waves in physical media. A string is modelled as two delay lines carrying waves in opposite directions; a bore is a single delay line with a reflective termination. Filters at the junction points and terminations model energy loss, dispersion, and reflection. This provides an extremely efficient implementation of physical models. Waveguides are a special case of the more general physical modeling class; the Karplus-Strong algorithm is a simplified single-pass waveguide.

Examples

The Yamaha VL1 (1994) synthesizer used waveguide models for woodwinds and bowed strings. Julius O. Smith’s website documents many waveguide instrument implementations in Matlab and Faust.

Assessment

What physical phenomenon does the delay line in a waveguide model represent? How does a waveguide model differ from the Karplus-Strong algorithm in its physical accuracy?