Electroglottography

Avaliação eletroglotográfica de mulheres disfônicas com lesão de massa

OBJETIVO: comparar os resultados da avaliação eletroglotográfica entre mulheres adultas com laudo otorrinolaringológico de nódulos vocais e presença de fenda glótica com mulheres sem alterações laríngeas. MÉTODO: trata-se de 20 mulheres, sendo 10 com exame otorrinolaringológico de nódulo vocal, associado à fenda glótica, e 10 com vozes avaliadas na análise perceptivo-auditiva como neutras e avaliação otorrinolaringológica sem alteração laríngea. A faixa etária variou de 27 a 55 anos, com média de 37,60 e 36,00 para grupo estudo e controle, respectivamente. O material de voz foi a emissão habitual da vogal sustentada /a/. Foram extraídas as medidas de quociente de contato, frequência fundamental, jitter, bem como a classificação e interpretação dos tipos de ondas e presença do joelho eletroglotográfico. A análise estatística foi realizada pelo teste Exato de Fisher e T de Student. RESULTADOS: todos os traçados foram classificados como tipo II (100%). Não foi observada diferença na presença ou ausência de joelho entre grupos. A média do quociente de contato foi de 42,52 e 45,56 para grupo estudo e controle, respectivamente. Apesar do menor valor para o grupo estudado, não houve diferença significante entre grupos. Houve relação estatisticamente significante entre grupos no que se refere à frequência fundamental e jitter. A média da frequência fundamental foi 193,18 e 211,69 e o valor médio de jitter foi 1,21 e 2,9 para o grupo estudo e controle, respectivamente. CONCLUSÃO: mulheres com lesão de massa nas pregas vocais apresentam maiores valores de jitter e menores valores para frequência fundamental eletroglotográfica.

Electroglottographic wavegrams: a technique for visualizing vocal fold dynamics noninvasively

A method for analyzing and displaying electroglottographic (EGG) signals (and their first derivative, DEGG) is introduced: the electroglottographic wavegram ("wavegram" hereafter). To construct a wavegram, the time-varying fundamental frequency is measured and consecutive individual glottal cycles are identified. Each cycle is locally normalized in duration and amplitude, the signal values are encoded by color intensity and the cycles are concatenated to display the entire voice sample in a single image, similar as in sound spectrography. The wavegram provides an intuitive means for quickly assessing vocal fold contact phenomena and their variation over time. Variations in vocal fold contact appear here as a sequence of events rather than single phenomena, taking place over a certain period of time, and changing with pitch, loudness and register. Multiple DEGG peaks are revealed in wavegrams to behave systematically, indicating subtle changes of vocal fold oscillatory regime. As such, EGG wavegrams promise to reveal more information on vocal fold contacting and de-contacting events than previous methods.

Automatic diagnosis of vocal fold paresis by employing phonovibrogram features and machine learning methods

The clinical diagnosis of voice disorders is based on examination of the rapidly moving vocal folds during phonation (f0: 80-300Hz) with state-of-the-art endoscopic high-speed cameras. Commonly, analysis is performed in a subjective and time-consuming manner via slow-motion video playback and exhibits low inter- and intra-rater reliability. In this study an objective method to overcome this drawback is presented being based on Phonovibrography, a novel image analysis technique. For a collective of 45 normophonic and paralytic voices the laryngeal dynamics were captured by specialized Phonovibrogram features and analyzed with different machine learning algorithms. Classification accuracies reached 93% for 2-class and 73% for 3-class discrimination. The results were validated by subjective expert ratings given the same diagnostic criteria. The automatic Phonovibrogram analysis approach exceeded the experienced raters' classifications by 9%. The presented method holds a lot of potential for providing reliable vocal fold diagnosis support in the future.

A comparison of different methods to measure the EGG contact quotient

The results from six published electroglottographic (EGG-based) methods for calculating the EGG contact quotient (CQEGG) were compared to closed quotients derived from simultaneous videokymographic imaging (CQKYM). Two trained male singers phonated in falsetto and in chest register, with two degrees of adduction in both registers. The maximum difference between methods in the CQEGG was 0.3 (out of 1.0). The CQEGG was generally lower than the CQKYM. Within subjects, the CQEGG co-varied with the CQkym, but with changing offsets depending on method. The CQEGG cannot be calculated for falsetto phonation with little adduction, since there is no complete glottal closure. Basic criterion-level methods with thresholds of 0.2 or 0.25 gave the best match to the CQKYM data. The results suggest that contacting and de-contacting in the EGG might not refer to the same physical events as do the beginning and cessation of airflow.

Measurement of vocal doses in speech: experimental procedure and signal processing

An experimental method for quantifying the amount of voicing over time is described in a tutorial manner. A new procedure for obtaining calibrated sound pressure levels (SPL) of speech from a head-mounted microphone is offered. An algorithm for voicing detection (kv) and fundamental frequency (F0) extraction from an electroglottographic signal is described. The extracted values of SPL, F0, and kv are used to derive five vocal doses: the time dose (total voicing time), the cycle dose (total number of vocal fold oscillatory cycles), the distance dose (total distance travelled by the vocal folds in an oscillatory path), the energy dissipation dose (total amount of heat energy dissipated in the vocal folds) and the radiated energy dose (total acoustic energy radiated from the mouth). The doses measure the vocal load and can be used for studying the effects of vocal fold tissue exposure to vibration.

Metallic Voice: Physiological and Acoustic Features

The metallic voice is usually confused with ring or nasality by singers and nontrained listeners, who are not used to perceptual vocal analysis. They believe a metallic voice results from a rise in fundamental frequency. A diagnostic error in this aspect may lead to lowering pitch, an incorrect procedure that could cause vocal overload and fatigue. The purpose of this article is to study the quality of metallic voice considering the correlation between information of the physiological and acoustic plans, based on a perceptive consensual assumption. Fiberscopic video pharyngolaryngoscopy was performed on 21 professional singers while speaking vowel [e]--in normal and metallic modes to observe muscular movements and structural changes of the velopharynx, pharynx, and larynx. Vocal samples captured simultaneously to the fiberscopic examination were acoustically analyzed. Frequency and amplitude of the first four formants (F(1), F(2), F(3), and F(4)) were extracted by means of linear predictor coefficients (LPC) spectrum and were statistically analyzed. Vocal tract adjustments such as velar lowering, pharyngeal wall narrowing, laryngeal rise, aryepiglottic, and lateral laryngeal constrictions were frequently found; there were no significant changes in frequency and amplitude of F(1) in the metallic voice; there were significant increases in amplitudes of F(2), F(3), and F(4) and in frequency for F(2); metallic voice perceived as louder was correlated to an increase in amplitude of F(3) and F(4). Physiological adjustments of velopharynx, pharynx, and larynx are combined in characterizing the metallic voice and can be acoustically related to changes in formant pattern.

An Exploration of Skin Acceleration Level as a Measure of Phonatory Function in Singing

Two kinds of fluctuations are observed in phonetogram recordings of singing. Sound pressure level (SPL) can vary due to vibrato and also due to the effect of open and closed vowels. Since vowel variation is mostly a consequence of vocal tract modification and is not directly related to phonatory function, it could be helpful to suppress such variation when studying phonation. Skin acceleration level (SAL), measured at the jugular notch and on the sternum, might be less influenced by effects of the vocal tract. It is explored in this study as an alternative measure to SPL. Five female singers sang vowel series on selected pitches and in different tasks. Recorded data were used to investigate two null hypotheses: (1) SPL and SAL are equally influenced by vowel variation and (2) SPL and SAL are equally correlated to subglottal pressure (P(S)). Interestingly, the vowel variation effect was small in both SPL and SAL. Furthermore, in comparison to SPL, SAL correlated weakly to P(S). SAL exhibited practically no dependence on fundamental frequency, rather, its major determinant was the musical dynamic. This results in a non-sloping, square-like phonetogram contour. These outcomes show that SAL potentially can facilitate phonetographic analysis of the singing voice.

Fundamental Frequency Histograms Measured by Electroglottography During Speech: A Pilot Study for Standardization

This study was designed to develop a database for the electroglottographic measurement of fundamental frequency (Fo) in normal subjects in running speech, for reference in the diagnosis and follow-up of dysphonic patients. A prospective pilot study included 20 healthy male volunteers without laryngeal disorder. Electroglottographic recordings of speaking Fo during connected speech (French) were obtained from two texts with different prosodic content. Fo histograms were sensitive to the variation of speaking Fo between both texts. Graphic representation of the range and distribution of the Fo of the speaker were designed as normalized Fo histograms with plot lines at 5th and 95th percentiles. Less than 5% variability of Fo histograms was recorded when recording more than 15 subjects. This pilot study designed a graphic display of standardized electroglottographic Fo measurements during the physiological condition of connected speech. As the degree of Fo variability depends on the phonetic contents of the text and on the language spoken, a separate histogram for normal subjects needs to be developed in each country or at least for each voice laboratory, with a standard, previously chosen text.

Effects of HearFones on speaking and singing voice quality

HearFones (HF) have been designed to enhance auditory feedback during phonation. This study investigated the effects of HF (1) on sound perceivable by the subject, (2) on voice quality in reading and singing, and (3) on voice production in speech and singing at the same pitch and sound level. Test 1: Text reading was recorded with two identical microphones in the ears of a subject. One ear was covered with HF, and the other was free. Four subjects attended this test. Tests 2 and 3: A reading sample was recorded from 13 subjects and a song from 12 subjects without and with HF on. Test 4: Six females repeated [pa:p:a] in speaking and singing modes without and with HF on same pitch and sound level. Long-term average spectra were made (Tests 1-3), and formant frequencies, fundamental frequency, and sound level were measured (Tests 2 and 3). Subglottic pressure was estimated from oral pressure in [p], and simultaneously electroglottography (EGG) was registered during voicing on [a:] (Test 4). Voice quality in speech and singing was evaluated by three professional voice trainers (Tests 2-4). HF seemed to enhance sound perceivable at the whole range studied (0-8 kHz), with the greatest enhancement (up to ca 25 dB) being at 1-3 kHz and at 4-7 kHz. The subjects tended to decrease loudness with HF (when sound level was not being monitored). In more than half of the cases, voice quality was evaluated "less strained" and "better controlled" with HF. When pitch and loudness were constant, no clear differences were heard but closed quotient of the EGG signal was higher and the signal more skewed, suggesting a better glottal closure and/or diminished activity of the thyroarytenoid muscle.

Final consonants and glottalization: new perspectives from Hanoi Vietnamese

The evolution from final obstruents to final glottal stop and then to rhyme glottalization (i.e. from /at/ to /a?/, then to /a'/) is a well-established general trend in the history of the Sino-Tibetan language family and beyond. It has further been shown by laryngoscopy that in three languages which retain the nonreleased syllable-final obstruents /p/, /t/ and /k/ (Standard Thai, and two Chinese dialects), these obstruents are often accompanied by a glottal stop. The present research raises the issue whether there is another typological possibility: can nonreleased final obstruents be accompanied consistently by modal phonation, without glottal stop? Analysis of electroglottographic recordings of 126 syllables in two carrier sentences spoken by 4 speakers shows that, in Hanoi Vietnamese, the final obstruents /p/, /t/ and /k/ are not accompanied by glottalization, and that the open quotient increases in the course of the syllable rhyme. Obstruent-final rhymes (which may carry either of two tones: D1 or D2) are compared with nasal-final rhymes which, under one of the tones (tone B2), are confirmed to be glottalized. Our finding is that tones D1 and D2 (i.e. obstruent-final rhymes) are both produced in modal voice, which shows that the typological paradigm of observed realizations of syllable-final obstruents must be enlarged. The discussion puts forward the hypothesis that the unusual association of segments and voice quality found in Hanoi Vietnamese is a strategy to maintain the opposition between B2-tone and D2-tone rhymes.

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.

Pathological voice quality assessment using artificial neural networks

This paper describes a prototype system for the objective assessment of voice quality in patients recovering from various stages of laryngeal cancer. A large database of male subjects steadily phonating the vowel /i/ was used in the study, and the quality of their voices was independently assessed by a speech and language therapist (SALT) according to their seven-point ranking of subjective voice quality. The system extracts salient short-term and long-term time-domain and frequency-domain parameters from impedance (EGG) signals and these are used to train and test an artificial neural network (ANN). Multi-layer perceptron (MLP) ANNs were investigated using various combinations of these parameters, and the best results were obtained using a combination of short-term and long-term parameters, for which an accuracy of 92% was achieved. It is envisaged that this system could be used as an assessment tool, providing a valuable aid to the SALT during clinical evaluation of voice quality.

Effects of speaking rate on the control of vocal fold vibration: clinical implications of active and passive aspects of devoicing

Stevens (1991) has suggested that, while speakers control glottal apertures in producing consonants, the buildup of intraoral pressure during an oral closure creates decreases in transglottal flow, which can, in itself, reduce or halt vocal fold vibrations. The object of this study was to determine whether speakers can take advantage of such pressure effects in controlling the voicing attributes of intervocalic stops. Intraoral pressure, vocal fold vibration (Lx portions of electroglottograms), and electromyographic (EMG) activity of the orbicularis oris inferior were monitored for 6 subjects while they produced at "slow," "normal," and "fast" speaking rates utterances containing intervocalic stops /p/ and /b/. Product-moment correlations between the intervocalic pressure rises and the amplitude contour of Lx showed strong negative relationships at normal-to-fast rates of speech. However, this relationship was not maintained at slower rates, where decreases in the amplitude of Lx sometimes occurred before the onset of EMG activity in the labial adductor. The findings suggest that, at normal-to-fast rates of speech, speakers can use the passive effects of pressure in controlling vocal fold vibration for stop consonants.

Strobophotoglottographic transillumination as a method for the analysis of vocal fold vibration patterns

The purpose of this exploratory study was to determine if laryngeal transillumination in combination with stroboscopy (strobophotoglottography; SPGG) is useful for (1) the visualization of vocal fold vibration (VFV) opening patterns, (2) the localization of initial vocal fold opening in horizontal glottal thirds (anterior, midmembranous, and posterior), (3) determination of the temporal correspondence of the so-called electroglottography (EGG)-knee and initial vocal fold separation, and, finally, (4) automatized quantitative measurements of glottal area function within endoscopic images. With stroboscopic transillumination, initial inferior vocal fold separation was detectable during the "closed" phase, where the vocal folds were still closed in the upper portion and therefore initial inferior vocal fold separation could not be visualized with usual laryngoscopy techniques. In the horizontal plane within similar fundamental frequencies in modal voice registers in two male subjects, localization of initial glottal opening depended on the voice types used (soft, normal, or pressed phonation). We found zipperlike posterior-to-anterior openings, initial midmembranous openings, initial anterior openings, as well as simultaneous initial opening of all three portions in the two healthy male adults examined. This technique proved to add temporal and spatial information to vocal fold opening patterns and extends our examination techniques to the very beginning of vocal fold opening at the inferior portion. Simultaneous electroglottogram tracking and comparison with bidirectionally illuminated stroboscopic images revealed a time-locked correspondence of the EGG-knee with the aforementioned initial inferior vocal fold separation. Bidirectional illumination combined with digital color extraction techniques allowed for image separation of subglottally and supraglottally illuminated structures. This facilitated vocal fold contour detection and automatized image processing, for example, for determination of glottal area function, and is considered to be a further step to objective automatized quantitative measurements within endoscopic images.

On pitch jumps between chest and falsetto registers in voice: data from living and excised human larynges

The paper offers a new concept of studying abrupt chest-falsetto register transitions (jumps) based on the theory of nonlinear dynamics. The jumps were studied in an excised human larynx and in three living subjects (one female and two male). Data from the excised larynx revealed that a small and gradual change in tension of the vocal folds can cause an abrupt change of register and pitch. This gives evidence that the register jumps are manifestations of bifurcations in the vocal-fold vibratory mechanism. A hysteresis was observed; the upward register jump occurred at higher pitches and tensions than the downward jump. Due to the hysteresis, the chest and falsetto registers can be produced with practically identical laryngeal adjustments within a certain range of longitudinal tensions. The magnitude of the frequency jump was measured as the "leap ratio" F0F:F0C (fundamental frequency of the falsetto related to that of the chest register) and alternatively expressed as a corresponding musical interval, termed the "leap interval." Ranges of this leap interval were found to be different for the three living subjects (0-5 semitones for the female, 5-10 and 10-17 for the two males, respectively). These differences are considered to reflect different biomechanical properties of the vocal folds of the examined subjects. A small magnitude of the leap interval was associated with a smooth chest-falsetto transition in the female subject.

Simultaneous videofluorographic and dual-channel electroglottographic registration of the vertical laryngeal position in various phonatory tasks

Simultaneous tracking of the vertical laryngeal position in various phonatory tasks was performed for 2 subjects (one male, one female) using dual-channel electroglottography (EGG) and videofluorography (videofluoroscopy). The tasks included phonation on [a:] with voluntary repeated (1) heightening and (2) lowering of the laryngeal position; alternation between [a:] and phonation on (3) [b], (4) [m], and (5) the voiced bilabial fricative [beta:]; and (6) production of the corner vowels [a, i, u]. EGG and videofluorography agreed about the direction of changes in the vertical laryngeal position in most cases. Most disagreements were found in the amount of changes. Reasons for the discrepancies, including, for example, changes in the resting position of the larynx and anteroposterior movements of the cartilages, are discussed. It can be concluded that dual-channel EGG is a valuable clinical and pedagogical tool for the analysis of the vertical displacement of larynx in well-specified phonatory tasks. The method should act most reliably on separately phonated vowels. Its applicability for studying laryngeal biomechanics more wholistically, however, is limited.

Global and local dimensions of vocal dynamics

The global embedding dimension (dE) and the local dynamical dimension (dL) are calculated from the microphone and electroglottographic (EGG) signals elicited from five healthy subjects and seven dysphonic subjects with laryngeal pathology during phonation of sustained/a/. The data from each pathologic subject contain at least one bifurcation and are divided into periodic and irregular segments for analysis. The dE values from both the microphone and EGG signals elicited from the healthy subjects indicate that a relatively small coordinate space can be used to reconstruct the attractor, with little residual noise. Consistent across all healthy subjects, three dominant degrees of freedom (dL) are found to govern local dynamics of the trajectories on the attractor. From the pathologic subjects, many of the dE values suggest the presence of a high-dimensional component in the signals. However, the noise does not completely obscure the deterministic dynamics of the source signal or prevent extraction of an optimal global embedding dimension. The data do not reveal consistent differences in degrees of freedom between healthy and pathologic phonation, or between different modes of pathologic phonation. However, the dL values suggest that the pathologic vocal fold vibration of these subjects, even highly irregular vibration, is governed locally by a low number of dominant degrees of freedom, sometimes no greater than those calculated from the signals of healthy subjects. Only in the cases of severe breathiness are the microphone and EGG signals sufficiently contaminated by noise to obscure any deterministic component.

Approximations of open quotient and speed quotient from glottal airflow and EGG waveforms: effects of measurement criteria and sound pressure level

Noninvasive measures of vocal fold activity are useful for describing normal and disordered voice production. Measures of open and speed quotient from glottal airflow and electroglottographic (EGG) waveforms have been used to describe timing events associated with vocal fold vibration. To date, there has been little consistency in the measurement criteria used to calculate quotient values. In this study, criteria of 20% and 50% were applied to the AC amplitude of glottal airflow and inverted EGG waveforms for measurement of open quotient. Criteria of 20%, 50%, and 80%, and a midslope criterion that segmented the waveform between 20% and 80% of the waveform amplitude, were used for the calculation of speed quotient. Subjects produced waveforms at sound pressure levels (SPL) of 70, 75, 80 and 85 dB. Results indicated that approximations of open quotient obtained from the glottal airflow waveform significantly decreased using both the 20% and 50% criteria as SPL increased from 80 to 85 dB. No significant changes were found in open quotient from the EGG waveform as a function of SPL. Results of speed quotient measures from the glottal airflow and EGG waveforms showed a generally increasing trend as SPL increased, although the differences were not statistically significant. The data suggest that the signal type, measurement criterion and SPL must be considered in interpreting quotient measures.

A physiological and acoustic study on voiced bilabial fricative/beta:/as a vocal exercise

The voiced bilabial fricative/beta:/has been used as a vocal exercise. The present study investigated the effects of the exercise on voice production and voice source. This study compared vowel phonation on the syllable /a:p/ with the production of the exercise and vowel phonation before and immediately after the exercise. The methods were (a) dual-channel electroglottography, from which the vertical laryngeal position was derived, (b) electromyography using surface electrodes, and (c) inverse filtering of the acoustic signal to obtain an estimate of the voice source. In the production of /beta:/ as compared with vowel phonation in most of the cases, the vertical laryngeal position seemed to be higher, the muscular activity of the larynx lower, and the slope of the voice source spectrum steeper. In vowel phonation after the exercise, the muscular activity seemed to be lower in most cases, although the voice source remained unchanged. This seems to indicate improved vocal economy.

Analysis of vocal fold function in the miniswine model

Correlation of the vocal fold vibratory pattern with the postoperative surgical wound should demonstrate to the laryngologist the critical depth of injury at which the functional voice would be adversely affected. An animal model was selected to study these changes. Twelve adult miniswine were operated on in this prospective study. The right true vocal fold was surgically altered; the left true vocal fold was the control. An interval of 6 weeks was allowed for healing, and then changes in vocal fold function were studied by stroboscopy, photography, voice recording, and electroglottography. Laryngectomy provided tissue for histopathological correlation. The results showed that injury at the junction of the lamina propria and vocalis muscle consistently caused significant vibratory dysfunction resulting in poor phonation.

Vocal stability and vocal tract configuration: an acoustic and electroglottographic investigation

Previous studies have reported differences in vocal fundamental frequency perturbation (jitter) and amplitude perturbation (shimmer) measures as a function of vowel type. However, it is not clear from those studies whether these effects derive from modifications in the shape of the vocal tract or from intrinsic vowel differences in mean fundamental frequency and vocal amplitude. The present study sought to address this issue using simultaneously obtained acoustic and electroglottographic (EGG) signals. Ten normal adult men and 10 normal adult women prolonged three maximally stable productions of the vowels [symbol: see text]. Vocal sound pressure level was maintained at 74 +/- 4 dB, while mean fundamental frequency was maintained at 110 and 220 Hz +/- 0.5 st for the male and female subjects, respectively. Results indicated that when vocal frequency and intensity are controlled, acoustic and EGG measures of mean jitter and shimmer do not show a significant vowel effect.