Ixone Arroabarren

Measurement of vibrato in lyric singers

In this paper, some digital signal processing techniques are proposed to measure the properties of the vibrato performed by lyric singers. From an audio record, three main signals are obtained which correlate with the acoustically perceived parameters: intonation, rate, and extent. The results obtained are much more informative than those previously reported by other authors who use less sophisticated techniques.

Instantaneous frequency and amplitude of vibrato in singing voice

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.

On the measurement of the instantaneous frequency and amplitude of partials in vocal vibrato

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

Inverse filtering in singing voice: a critical analysis

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

Vibrato in singing voice: the link between source-filter and sinusoidal models

The application of inverse filtering techniques for high-quality singing voice analysis/synthesis is discussed. In the context of source-filter models, inverse filtering provides a noninvasive method to extract the voice source, and thus to study voice quality. Although this approach is widely used in speech synthesis, this is not the case in singing voice. Several studies have proved that inverse filtering techniques fail in the case of singing voice, the reasons being unclear. In order to shed light on this problem, we will consider here an additional feature of singing voice, not present in speech: the vibrato. Vibrato has been traditionally studied by sinusoidal modeling. As an alternative, we will introduce here a novel noninteractive source filter model that incorporates the mechanisms of vibrato generation. This model will also allow the comparison of the results produced by inverse filtering techniques and by sinusoidal modeling, as they apply to singing voice and not to speech. In this way, the limitations of these conventional techniques, described in previous literature, will be explained. Both synthetic signals and singer recordings are used to validate and compare the techniques presented in the paper.

Voice Production Mechanisms of Vocal Vibrato in Male Singers

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

Effect of the glottal source and the vocal tract on the partials amplitude of vibrato in male voices

In this paper the production of vocal vibrato is investigated. The most relevant features of the acoustical vibrato signal, frequency and amplitude variations of the partials, will be related to the voice production features, glottal source (GS) and vocal tract response (VTR). Unlike previous related works, in this approach, the effect on the amplitude variations of the partials of each one of the above-mentioned voice production features will be identified in recordings of natural singing voice. Moreover, we will take special care of the reliability of the measurements, and, to this aim, a noninteractive vibrato production model will be also proposed in order to describe the vibrato production process and, more importantly, validate the measurements carried out in natural vibrato. Based on this study, it will be shown that during a few vibrato cycles, the glottal pulse characteristics, as well as the VTR, do not significantly change, and only the fundamental frequency of the GS varies. As a result, the pitch variations can be attributed to the GS, and these variations, along with the vocal tract filtering effect, will result in frequency and amplitude variations of the acoustic signal partials.

Generation of low crest-factor band-pass excitation signals by spectral profile shaping

In this communication, a novel procedure is proposed to generate band-pass low crest-factor signals for system response characterization. The concept of frequency modulation is used combined with an iteration procedure to trade spectrum ripple and crest-factor.

Application of multitone signals in room acoustics measurements

This paper addresses the problem of measuring the acoustic frequency response of auditoria and loudspeaker characterization. The difficulty of the problem is illustrated with a number of measurements performed using different methods and equipment. The use of multitone signals both uniformly and logarithmically spaced is proposed to obtain fast and reproducible measurements.