A SIMPLE, ACCURATE WALL LOSS FILTER FOR ACOUSTIC TUBES
Jonathan S. Abel, Santa Cruz, Tamara Smyth, Julius O. Smith · 2003
This research presents a uniform approximation to the formulas of Benade and Keefe for the propagation constant of a cylindrical tube, valid for all tube radii and frequencies in the audio range. Based on this approximation, a simple expression is presented for a filter which closely matches the thermoviscous loss filter of a tube of specified length and radius at a given sampling rate. The form of this filter and the simplicity of coefficient calculation make it particularly suitable for real-time music applications where it may be desirable to have tube parameters such as length and radius vary during performance. sampling rate. All filter design methods have comparable accuracy for a given order of digital filter, while the shelf filter cascade has the advantage of design simplicity and is nicely parameterized for time varying tube geometries.