Implementation of a continuously variable delay line by crossfading between several tap delays
Résumé
Delay lines are ubiquitous in computer music applications: they are used to create audio effects or to simulate the sound propagation of moving sources. When one wants to synthesize a delay which varies over time, two main strategies are typically implemented: a) by using a “fractional” delay line, which simulates a non-integer delay based on an interpolator filter; or b) by applying a crossfade between the initial delay and the new desired delay value. These two techniques may induce pitch shift and/or spectral artifacts which are not tolerable in certain applications such as spatial reproduction by wavefield synthesis (WFS). In this article we propose a new method for creating a continuously variable delay line; the technique is an extension of the crossfade delay technique which exploits a superposition of several “auxiliary” tap delays whose times and gains are determined by a methodology similar to fractional delay interpolating filters. We show that it is thus possible to reduce coloration artifacts, at the expense of a higher computational cost.
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