Vibrato constitutes one of the most interesting features of singing voice. It has been the topic of interest of many researchers in different knowledge areas such as acoustics, physiology, and psychoacoustics. In spite of this, some basic aspects related to vibrato production still remain unclear, such as the origin of its most relevant acoustical features, (frequency and amplitude variations of the partials) or the relevance of recently identified physiological effects, such as pitch synchronous variations of the voice organ. In this paper, a novel interactive vibrato production model will be proposed in order to accomplish a realistic voice production description, in such a way that the source-tract interaction will be included in the prediction model. This will allow us to identify, from the acoustical signal, additional effects typical of vocal vibrato, such as slight pitch synchronous variations of the vocal tract response, as well as to analyze the relationship between the acoustical features of vibrato and the voice production elements

Inverse filtering provides a noninvasive method to extract the voice source, and thus get insight into voice quality. Although this technique is widely used in speech analysis, this is not the case in singing voice, where its use has been even questioned by some authors. In this paper, a comparative study of some representative inverse filtering techniques will be presented in order to identify their main limitations in singing voice analysis. After a rough classification of the inverse filtering techniques, three representative procedures will be selected in order to cover all kind of approaches, and then evaluated taking into account two relevant features: their fundamental frequency limitation, and their sensitivity to the source-tract interaction. To make this comparative study possible, an interactive source-filter model we propose will be used such that the source-tract interaction can be controlled. In this way, the above-mentioned effects will be evaluated based on a simulation analysis, with a realistic singing production model. Natural singing voice results will be also reported to validate the simulations. This study will allow concluding that the main limiting aspect of inverse filtering in singing voice analysis is the fundamental frequency limitation, whereas the source-tract interaction represents a less relevant issue

In this paper, we analyze some methodological and practical grounds affecting a correct estimation of the instantaneous amplitude (IA) and instantaneous frequency (IF) of the partials of vocal vibrato signals. This particular class of acoustical signals can be described as a set of harmonics, or partials, whose amplitude and frequency vary with time following a particular pattern. The interest in the correct measurement of these two magnitudes stems from the fact that they are widely used to extract more information about the production mechanisms of this vocal effect, and even the singing voice. Focusing on the estimation of these magnitudes from the signal processing point of view, the estimation of the IA and the IF of a partial represents a practical example for the more general problem of the AM-FM decomposition of a bandpass signal, which has received considerable attention by the Time-Frequency community. With this in mind, this work will investigate the most appropriate AM-FM decomposition of the partials, and how it is affected by the reverberation present in recordings. A mathematical description of the effect of reverberation on the measurement will be given. It will be shown that the measurement of the IA and the IF of the partials will be corrupted by reverberation regardless of the employed estimation method

We investigate the relationship between the instantaneous amplitude (IA) and the instantaneous frequency (IF) of vibrato signals in the singing voice. It is shown that this relationship is of great value in obtaining information about the vocal tract model. However, to make this analysis possible, it is necessary to cope with two basic limitations: reverberation in recordings, which shows up as multiharmonicity in each partial, and the phase effect of vocal tract formants which distort the instantaneous frequency of some partials.

Trabajo presentado al 8th European Conference on Speech Communication and Technology (EUROSPEECH 2003 - INTERSPEECH 2003), Ginebra (Suiza), 1-4 de septiembre de 2003

Trabajo presentado al 8th European Conference on Speech Communication and Technology (EUROSPEECH 2003 - INTERSPEECH 2003), Ginebra (Suiza), 1-4 de septiembre de 2004