D4C, a band-aperiodicity estimator for high-quality speech synthesis

An algorithm is proposed for estimating the band aperiodicity of speech signals, where “aperiodicity” is defined as the power ratio between the speech signal and the aperiodic component of the signal. Since this power ratio depends on the frequency band, the aperiodicity should be given for several frequency bands. The proposed D4C (Definitive Decomposition Derived Dirt-Cheap) estimator is based on an extension of a temporally static group delay representation of periodic signals. In this paper, the principle and algorithm of D4C are explained, and its effectiveness is discussed with reference to objective and subjective evaluations. Evaluation results indicate that a speech synthesis system using D4C can synthesize natural speech better than ones using other algorithms.