DAFX: Digital Audio Effects, Second Edition

9.4 Examples of Adaptive DAFX

As explained in this chapter's introduction, several effects already made use of adaptive control a long time before recent studies tended to generalize this concept to all audio effects [VA01, ABL+03]. Such effects were developed for technical or musical purposes, as answers to specific needs (e.g., auto-tune, compressor, cross-synthesis). Using the framework presented in this chapter, we can now ride on the adaptive wave, and present old and new adaptive effects in terms of: their form, the sound features that are used, the mapping of sound features to effect control parameters, the modifications of implementation techniques that are required, and the perceptual effect of the ADAFX.

9.4.1 Adaptive Effects on Loudness

Adaptive Sound-level Change

By controlling the sound level from a sound feature, we perform an amplitude modulation with a signal which is not monosinusoidal. This generalizes compressor/expander, noise gate/limiter, and cross-duking, which all are specific cases in terms of sound-feature extraction and mapping. Adaptive amplitude modulation controlled by c(n) provides the following signal

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By deriving c(n) from the sound-intensity level, one obtains compressor/expander and noise gate/limiter. By using the voiciness v(n) ∈ [0, 1] and a mapping law, one obtains a ‘voiciness gate,’ which is a timbre effect that removes voicy sounds ...