Nathalie Henrich

On the use of the derivative of electroglottographic signals for characterization of nonpathological phonation

Electroglottography is a common method for providing noninvasive measurements of glottal activity. The derivative of the electroglottographic signal, however, has not attracted much attention, although it yields reliable indicators of glottal closing instants. The purpose of this paper is to provide a guide to the usefulness of this signal. The main features that are to be found in this signal are presented on the basis of an extensive analysis of a database of items sung by 18 trained singers. Glottal opening and closing instants are related to peaks in the signal; the latter can be used to measure glottal parameters such as fundamental frequency and open quotient. In some cases, peaks are doubled or imprecise, which points to special (but by no means uncommon) glottal configurations. A correlation-based algorithm for the automatic measurement of fundamental frequency and open quotient using the derivative of electroglottographic signals is proposed. It is compared to three other electroglottographic-based methods with regard to the measurement of open quotient in inverse-filtered derived glottal flow. It is shown that agreement with the glottal-flow measurements is much better than most threshold-based measurements in the case of sustained sounds.

Glottal open quotient in singing: Measurements and correlation with laryngeal mechanisms, vocal intensity, and fundamental frequency

This article presents the results of glottal open-quotient measurements in the case of singing voice production. It explores the relationship between open quotient and laryngeal mechanisms, vocal intensity, and fundamental frequency. The audio and electroglottographic signals of 18 classically trained male and female singers were recorded and analyzed with regard to vocal intensity, fundamental frequency, and open quotient. Fundamental frequency and open quotient are derived from the differentiated electroglottographic signal, using the DECOM (DEgg Correlation-based Open quotient Measurement) method. As male and female phonation may differ in respect to vocal-fold vibratory properties, a distinction is made between two different glottal configurations, which are called laryngeal mechanisms: mechanism 1 (related to chest, modal, and male head register) and mechanism 2 (related to falsetto for male and head register for female). The results show that open quotient depends on the laryngeal mechanisms. It ranges from 0.3 to 0.8 in mechanism 1 and from 0.5 to 0.95 in mechanism 2. The open quotient is strongly related to vocal intensity in mechanism 1 and to fundamental frequency in mechanism 2.

Laryngeal Vibratory Mechanisms: The Notion of Vocal Register Revisited

This study, focused on the laryngeal source level, introduces the concept of laryngeal vibratory mechanism. Human phonation is characterized by the use of four laryngeal mechanisms, labeled M0-M3, as evidenced by the electroglottographic (EGG) study of the transition phenomena between mechanisms with a population of men and women, trained and untrained singers. Macroscopic and local descriptions of the EGG signal are analyzed during the production of glissandos and held notes with different mechanisms. The transition from one mechanism to another of higher rank is characterized by a jump in frequency, a reduction of EGG amplitude, and a change in the shape of the derivative of the EGG (which may correspond to a reduction of the vibratory mass). These characteristics are used to identify a transition between two mechanisms, in complement with acoustic spectrographic analyses. The pitches of transitions between the two main mechanisms M1 and M2 and the range of the frequency-overlap region are described in detail. The notion of vocal register is revisited in the light of these concepts of laryngeal mechanism. The literature on vocal registers is reviewed, and it is shown that the confusion often cited with respect to this notion may be related to the heterogeneity of the approaches and methods used to describe the phenomena and to the multiplicity of descriptors. Therefore, the terminology of the registers is organized depending on their relation to the four laryngeal vibratory mechanisms.

Mirroring the voice from Garcia to the present day: some insights into singing voice registers.

Starting from Garcias definition, the historical evolution of the notion of vocal registers from then until now is considered. Even though much research has been carried out on vocal registers since then, the notion of registers is still confused in the singing voice community, and defined in many different ways. While some authors consider a vocal register as a totally laryngeal event, others define it in terms of overall voice quality similarities. This confusion is reflected in the multiplicity of labellings, and it lies in the difficulty of identifying and specifying the mechanisms distinguished by these terms. The concept of laryngeal mechanism is then introduced, on the basis of laryngeal transition phenomena detected by means of electroglottography. It helps to specify at least the laryngeal nature of a given singing voice register. On this basis, the main physiological, acoustic, and perceptual characteristics of the most common singing voice registers are surveyed.

Vocal tract adjustments in the high soprano range.

Twelve sopranos with different levels of expertise (4 nonexperts, 4 advanced, 4 professionals) sustained pitches from A4 ( approximately 440 Hz) to their highest pitch (ranging from C6 to D7, i.e., from approximately 1000 to 2300 Hz). The frequencies of their first two vocal tract resonances (R1 and R2) were measured by broadband excitation at the mouth and compared with the voice harmonics (f(0), 2f(0), etc). Lip articulation was measured from simultaneous video recordings. Adjustment of R1 near to f(0) (R1:f(0) tuning) was observed below C6 to D6 ( approximately 1000-1200 Hz) for both expert and non-expert singers. Experts began this tuning at lower pitches. Some singers combine R2:2f(0) adjustment with R1:f(0) tuning. Some singers increased mouth area with increasing pitch over the whole R1:f(0) tuning range. Other singers showed this strategy on the higher part of the R1:f(0) range only, and used another, as yet unidentified, articulatory strategy on the lower part. To achieve very high pitches, some singers extended the range of R1:f(0) tuning as far as E6 to F#6 ( approximately 1300-1500 Hz) while others adjusted R2 near f(0) over the highest pitch range.

A comparative study of pitch extraction algorithms on a large variety of singing sounds

The problem of pitch tracking has been extensively studied in the speech research community. The goal of this paper is to investigate how these techniques should be adapted to singing voice analysis, and to provide a comparative evaluation of the most representative state-of-the-art approaches. This study is carried out on a large database of annotated singing sounds with aligned EGG recordings, comprising a variety of singer categories and singing exercises. The algorithmic performance is assessed according to the ability to detect voicing boundaries and to accurately estimate pitch contour. First, we evaluate the usefulness of adapting existing methods to singing voice analysis. Then we compare the accuracy of several pitch-extraction algorithms, depending on singer category and laryngeal mechanism. Finally, we analyze their robustness to reverberation.

Influence of a constriction in the near field of the vocal folds: Physical modeling and experimental validation

The involvement of the ventricular folds is often observed in human phonation and, in particular, in pathological and or some throat-singing phonation. This study aims to explore and model the possible aerodynamic interaction between the ventricular and vocal folds using suitable in vitro setups allowing steady and unsteady flow conditions. The two experimental setups consist of a rigid and a self-oscillating vocal-fold replica, coupled to a downstream rigid ventricular-fold replica in both cases. A theoretical flow modeling is proposed to quantify the aerodynamic impact of the ventricular folds on the pressure distribution and thereby on the vocal-fold vibrations. The mechanical behavior of the vocal folds is simulated by a distributed model accounting for this impact. The influence of the ventricular constriction is measured in both flow conditions and compared to the model outcome. This study objectively evaluates the additional pressure drop implied by the presence of a ventricular constriction in the larynx. It is demonstrated that such constriction can either facilitate or impede the glottal vibrations depending on the laryngeal geometrical configuration. The relevance of using static or dynamic vocal-fold replicas is discussed.

Vocal tract resonances in singing: Strategies used by sopranos, altos, tenors, and baritones

The first two vocal tract resonances (R1 and R2) of 22 classically trained sopranos, altos, tenors, and baritones were measured while they sang four different vowels over their normal pitch range. The resonances of the tract and the harmonics of the voice were measured simultaneously by injecting a broadband acoustic current into the tract at their mouth. Sopranos were found to tune R1 close to the fundamental frequency f(0) (R1:f(0) tuning) over at least part of their upper range for all vowels studied, particularly when f(0) was around or above the value of R1 for speech. Additionally, most sopranos employed R2:2f(0) tuning over some of their range, often simultaneously with R1:f(0) tuning. Altos used R1:f(0) tuning for vowels having lower values of R1 in speech, but can switch to R1:2f(0) tuning in the lower part of their range. Tenors and baritones generally used R1:2f(0) and R1:3f(0) tunings over part of their range and employed a number of different tunings to higher harmonics at lower pitch. These results indicate that singers can repeatedly tune their resonances with precision, and that there can be considerable differences in the resonance strategies used by individual singers, particularly for voices in the lower ranges.

Vocal fold and ventricular fold vibration in period-doubling phonation: physiological description and aerodynamic modeling.

Occurrences of period-doubling are found in human phonation, in particular for pathological and some singing phonations such as Sardinian A Tenore Bassu vocal performance. The combined vibration of the vocal folds and the ventricular folds has been observed during the production of such low pitch bass-type sound. The present study aims to characterize the physiological correlates of this acoustical production and to provide a better understanding of the physical interaction between ventricular fold vibration and vocal fold self-sustained oscillation. The vibratory properties of the vocal folds and the ventricular folds during phonation produced by a professional singer are analyzed by means of acoustical and electroglottographic signals and by synchronized glottal images obtained by high-speed cinematography. The periodic variation in glottal cycle duration and the effect of ventricular fold closing on glottal closing time are demonstrated. Using the detected glottal and ventricular areas, the aerodynamic behavior of the laryngeal system is simulated using a simplified physical modeling previously validated in vitro using a larynx replica. An estimate of the ventricular aperture extracted from the in vivo data allows a theoretical prediction of the glottal aperture. The in vivo measurements of the glottal aperture are then compared to the simulated estimations.

Resonance strategies used in Bulgarian women's singing style: A pilot study

Are the characteristic timbre and loudness of Bulgarian womens singing related to tuning of resonances of the vocal tract? We studied an Australian female singer, who practises and teaches Bulgarian singing technique. Two different vocal qualities of this style were studied. The louder teshka is characterized by a sonorous voice production. The less loud leka has a smoother timbre that is closer to that of the head voice register. Six vowels in each of teshka, leka and the subjects ‘normal’ (i.e. Western rather than Bulgarian) style were studied. The acoustic resonances of the singers vocal tract were measured directly during singing by injecting a synthesized, broad-band acoustic current. This singer does not use resonance tuning consistently in her classical Western style. However, in both teshka and leka, she tunes the first tract resonance close to the second harmonic of the voice for most vowels. This tuning boosts the power output in the radiation field for that harmonic. This tuning also contributes to the very strong second harmonic which is a characteristic of the timbre identified as the Bulgarian style.