On the Application of RLS Adaptive Filtering for Voice Pitch Modification

Rafael C. D. de Paiva; Luiz W. P. Biscainho; Sergio L. Netto
DAFx-2007 - Bordeaux
This paper presents a pitch modification scheme, based on the recursive least-squares (RLS) adaptive algorithm, for speech and singing voice signals. The RLS filter is used to determine the linear prediction (LP) model on a sample-by-sample framework, as opposed to the LP-coding (LPC) method, which operates on a block basis. Therefore, an RLS-based approach is able to preserve the natural subtle variations on the vocal tract model, avoiding discontinuities in the synthesized signal and the inherent frame-delay associated to classic methods. The LP residual is modified in the synthesis stage in order to generate the output signal. Listening tests verify the overall quality of the synthesized signal using the RLS approach, indicating that this technique is suitable for realtime applications.