Electroglottogram Research Articles

Grouping Intrinsic Mode Functions and Residue for Pathological Classifications via Electroglottograms

The electroglottogram (EGG) is a signal used for measuring the change of the relative contact area in the vocal cord during the throat production. In the recent years, the low cost and the non-invasive applications have been derived. Hence, the EGG has been applied in various science, engineering and medical fields such as in the basic voice science including the phonetics, the singing and the hearing as well as in the speech and the language therapy and the related clinical works including the voice production physiology, the swallowing and the psychology. However, the pathological classifications using the EGGs usually yield the poor performances. This is because the EGGs are required to decompose into the various components for extracting the features for performing the classifications. Nevertheless, the total numbers of the components decomposed by some time frequrncy representation such as the empirical mode decomposition (EMD) for different EGGs are different. Hence, the dimension of the feature vectors extracted from different EGGs is different. This introduces to the difficulty for building a machine learning model for performing the classification. This paper is to address this issue. This paper proposes a method for grouping the intrinsic mode functions (IMFs) and the residue obtained by applying the EMD to the EGGs for classifying between the healthy subjects and the pathological subjects. More precisely, this paper proposes a clustering based method to group the IMFs and the residue so that the total numbers of the grouped IMFs of different EGGs are the same. First, the IMFs and the residue of the EGGs are catergorized into a desired number of groups based on their correlation coefficients. Second, the IMFs or the residue in each group are summed together to obtain the grouped IMF. Third, the mean frequency and the first formant of each grouped IMF are computed. Finally, a random forest is employed for performing the classification. To our best knowledge, this joint EMD and clustering based method is firstly proposed to preform the pathological voice detection. The computer numerical simulations are conducted using the online availiable Saarbrücken voice database. Here, five cross validations have been performed. The mean accuracy, the mean specificity and the mean sensitivity among these five validations are 86.98, 79.92 and 91.57, respectively. The standard deviation of the accuracy, the specificity and the sensitivity among these five validations are ±2.00%, ±3.71% and ±2.13%, respectively. The simulation results show that our proposed method outperforms the common EGG or speech processing based methods. This paper proposes a clustering based method for grouping the IMFs and the residue for performing the pathological classifications via the EGGs. The grouping criterion is based on the correlation coefficients. It is found that our proposed method can achieve the highest classifications for the majority signal to noise ratios compared to the state of the arts methods. • This paper proposes a clustering based method for grouping the IMFs and the residue. • It applies to classify between the healthy and the pathological subjects. • The total numbers of the grouped IMFs of different EGGs are the same. • The mean frequency and the first formant of each grouped IMF are computed. • A random forest is employed for performing the classification.

How Much Loading Does Water Resistance Voice Therapy Impose on the Vocal Folds? An Experimental Human Study

Water resistance voice therapy applies phonation into water through a tube. This study investigates how strenuous this therapy can be for the vocal folds in terms of impact stress (IS). It further examines whether it is possible to estimate the IS using the contact quotient (CQ) and maximum derivative from an electroglottogram (EGG). Experimental study. A male participant sustained a rounded back vowel [u:] or [o:] at a comfortable speaking pitch and loudness, and phonated into a silicone "Lax Vox" tube submerged 2 cm in water. High-speed videolaryngoscopy was performed with a rigid scope. Oral air pressure (Poral) was registered in a mouthpiece through which an endoscope was inserted into the larynx. An EGG was recorded. The CQEGG from the EGG and the closed quotient from the glottal width (CQarea) increased, while the maximum glottal amplitude and absolute value of derivative minimum (dmin) and also the derivative maximum from the EGG decreased for phonation into water. Normalized amplitude quotient from the glottal width variation also decreased but the change was not significant. Based on the glottal area findings, water resistance therapy does not seem to increase vocal fold loading (in terms of increased IS) even if the increase of CQarea, and CQEGG suggest so. CQEGG may qualitatively correspond to that of area, but the reliability of CQ (from the glottal area or the EGG) and the maximum derivative from the EGG as estimates of IS in semiocclusion exercises warrant further studies.

Development of simulated emotion speech database for excitation source analysis

The work presented in this paper is focused on the development of a simulated emotion database particularly for the excitation source analysis. The presence of simultaneous electroglottogram (EGG) recordings for each emotion utterance helps to accurately analyze the variations in the source parameters according to different emotions. The work presented in this paper describes the development of comparatively large simulated emotion database for three emotions (Anger, Happy and Sad) along with neutrally spoken utterances in three languages (Tamil, Malayalam and Indian English). Emotion utterances in each language are recorded from 10 speakers in multiple sessions (Tamil and Malayalam). Unlike the existing simulated emotion databases, instead of emotionally neutral utterances, emotionally biased utterances are used for recording. Based on the emotion recognition experiments, the emotions elicited from emotionally biased utterances are found to show more emotion discrimination as compared to emotionally neutral utterances. Also, based on the comparative experimental analysis, the speech and EGG utterances of the proposed simulated emotion database are found to preserve the general trend in the excitation source characteristics (instantaneous F0 and strength of excitation parameters) for different emotions as that of the classical German emotion speech-EGG database (EmoDb). Finally, the emotion recognition rates obtained for the proposed speech-EGG emotion database using the conventional mel frequency cepstral coefficients and Gaussian mixture model based emotion recognition system, are found to be comparable with that of the existing German (EmoDb) and IITKGP-SESC Telugu speech emotion databases.

Investigation of the relationship between electroglottogram waveform, fundamental frequency, and sound pressure level using clustering

Although it has been shown in previous research (Orlikoff, 1991; Henrich etal, 2005; Kuang etal, 2014; Awan, 2015) that there exists a relationship between the electroglottogram (EGG) waveform and the acoustic signal, this relationship is still not fully understood. To investigate this relationship, the EGG and acoustic signals were measured for four male amateur choir singers who each produced eight consecutive tones of increasing and decreasing vocal intensity. The EGG signals were processed cycle-synchronously to obtain the discrete Fourier transform, and the data were used as an input to a clustering algorithm. The acoustic signal was analyzed in terms of sound pressure level (dB SPL) and fundamental frequency (fo) of vibration, and the results of both EGG and acoustic analysis were depicted on a two-dimensional plane with fo on the x-axis and SPL on the y-axis. All the subjects were seen to have a weak, near-sinusoidal EGG waveform in their lowest SPL range, whereas increase in SPL coincided with progressive enrichment in harmonic content of the EGG waveforms. The results of the clustering were additionally used to classify waveforms across subjects to enable inter-subject comparisons and assessment of individual strategies of exploring the fo-SPL dimensions. In these male subjects, the EGG waveform shape appeared to vary with SPL and to remain essentially constant with fo over one octave.

Contact Quotient Versus Closed Quotient: A Comparative Study on Professional Male Singers

The term "closed quotient" is frequently used for data derived both from inverse filtering and from electroglottography. In the former case, it is defined as the ratio between the closed phase and the period, as measured in flow glottograms (FLOGG), whereas in the latter case, it is defined as the time interval between the falling and rising parts of the electroglottogram (EGG), measured at some percentage of the peak-to-peak amplitude. The study aims at analyzing differences between EGG- and FLOGG-based closed quotients and their relationships with voice source parameters. Comparative study. FLOGG- and EGG-based measures collected from five professional male singers were compared, under different pitch and loudness conditions. Compared with the FLOGG-based quotient, the EGG-based quotient (i) varied more between subjects, (ii) presented greater values, (iii) varied less with subglottal pressure, (iv) varied less with the normalized amplitude quotient (ie, the ratio between the flow pulse amplitude and the product of period and maximum flow declination rate), and (v) varied less with the relative amplitude of the voice source fundamental. Although positively related, FLOGG- and EGG-based closed quotients differ and must not be confused.

Formant and Voice Source Properties in Two Male Kunqu Opera Roles: A Pilot Study

Objective: This investigation analyzes flow glottogram and electroglottogram (EGG) parameters as well as the relationship between formant frequencies and partials in two male Kunqu Opera roles, Colorful face (CF) and Old man (OM). Participants and Methods: Four male professional Kunqu Opera singers volunteered as participants, 2 singers for each role. Using inverse filtering of the audio signal flow glottogram parameters and formant frequencies were measured in each note of scales. Two EGG parameters, contact quotient (CoQ) and speed quotient, were measured. Results: Formant tuning was observed only in 1 of the OM singers and appeared in a pitch range lower than the passaggio range of Western male opera singers. Both the CF and the OM role singers showed high CoQ values and low values of the normalized amplitude quotient in singing. For 3 of the 4 singers CoQ and the level difference between the first and second partials showed a positive and a negative correlation with fundamental frequency (F0), respectively. Conclusions: Formant tuning may be applied by a singer of the OM role, and both CF and OM role singers may use a rather pressed type of phonation, CF singers more than OM singers in the lower part of the pitch range. Most singers increased glottal adduction with rising F0.

Voice disorders assessed by (cross-) Sample Entropy of electroglottogram and microphone signals

The quantitative analysis of vocal disorders by nonlinear signal processing methods has been extensively used in the last two decades. In this work, two algorithms for nonlinear time-series analysis, Sample Entropy and cross-Sample Entropy, are used on electroglottogram (EGG) and microphone (MIC) signals recorded from 51 normal and 80 dysphonic subjects, to obtain summary measures of voice disorders through SampEn and cross-SampEn indices. Such parameters quantify, respectively, the degree of irregularity (in the sense of self-dissimilarity) within a time-series and of asynchrony (in the sense of cross-dissimilarity) between two distinct time-series. The aims of this work are: to determine if statistically significant differences in terms of signal irregularity quantified by SampEn occur between normal and pathological subjects, investigating whether or not such differences can be equally seen in EGG and MIC; to assess if cross-SampEn reveals different degrees of asynchrony between EGG and MIC signals in the two groups. Results show that SampEn in pathological subjects is higher than in normal subjects for both EGG and MIC time-series, with a statistically significant difference detectable from both signals (Pe<10−4 for EGG and Pe<10−7 for MIC). Cross-SampEn exhibits a statistically significant difference too, showing a higher degree of cross-dissimilarity between EGG and MIC time-series for pathological subjects (Pe<10−4). In conclusion, SampEn and cross-SampEn well quantify the increase of complexity of both EGG and MIC signals and the decrease of their cross-similarity in presence of vocal disorders. Thanks to the complementarity of nonlinear indicators to the traditionally considered linear ones, SampEn and cross-SampEn appear as suitable candidates to enter the pool of approaches to investigate speech pathologies and to obtain potentially new insights on their nature.

Laryngeal movements in stutterers

Background: The etiology of stuttering is a puzzle. Abnormal laryngeal movements have been assumed to be a cause of stuttering by many researchers. We aimed at comparing the laryngeal functions of stutterers using electroglottogram (EGG) and vocal tract functioning using formant frequency analysis. Materials and Methods: We compared the acoustic and electroglottographic parameters in the phonation of stutterers between the age range of 15-25 years and normal subjects matched for age and sex. Results and Discussion: All the electroglottographic parameters of stutterers differed from that of normal speaking subjects which is indicative of difficulty in adjustment of the laryngeal gestures for speech in stutterers. There was no significant difference between the stutterers and non-stutterers in terms of formant frequencies. Similar formant frequencies in stutterers and normal speakers and abnormal electroglottographic parameters are suggestive of abnormal laryngeal movements and normal vocal tract functioning in stutterers.

Electroglottographic contact quotient in different phonation types using different amplitude threshold levels

Contact quotient (CQ), measured by electroglottogram (EGG), is a ratio which illustrates the duration of vocal fold contact during one vocal fold period. In the present study CQEGG was calculated from a sustained vowel phonation in three different phonation types (breathy, normal, pressed) at three amplitude threshold levels (25%, 35%, 50%). CQEGG values were compared with experts’ perceptual evaluation of the firmness of phonation. The contact time of the vocal folds differed significantly between the different phonation types at all threshold levels (P < 0.01). Perceptual evaluation correlated best with CQEGG at threshold levels 25% and 35%. The results of the linear regression model suggested that by using threshold level 25% the effect of F0 and SPL on CQEGG were not significant.

Open Quotient Measurements Based on Multiscale Product of Speech Signal Wavelet Transform

This paper describes a multiscale product method (MPM) for open quotient measure in voiced speech. The method is based on determining the glottal closing and opening instants. The proposed approach consists of making the products of wavelet transform of speech signal at different scales in order to enhance the edge detection and parameter estimation. We show that the proposed method is effective and robust for detecting speech singularity. Accurate estimation of glottal closing instants (GCIs) and opening instants (GOIs) is important in a wide range of speech processing tasks. In this paper, accurate estimation of GCIs and GOIs is used to measure the local open quotient (Oq) which is the ratio of the open time by the pitch period. Multiscale product operates automatically on speech signal; the reference electroglottogram (EGG) signal is used for performance evaluation. The ratio of good GCI detection is 95.5% and that of GOI is 76%. The pitch period relative error is 2.6% and the open phase relative error is 5.6%. The relative error measured on open quotient reaches 3% for the whole Keele database.

Quantifying aberrant phonation using approximate entropy in electrolaryngography

Vocal fold vibration during vowel phonation can be used to characterise voice quality. This vibration can be measured using a laryngograph, which produces a waveform of highly correlated trans-larynx impedance variations, collectively termed the electroglottogram (EGG). Using approximate entropy (ApEn) in the EGG spectral domain, earlier work has been able to explain the meaning of “voice normality” and also to begin quantifying the impact that radiotherapy treatment has on the voicing of larynx cancer patients. In this paper ApEn is used to quantify pathological voicing in radiotherapy patients using the EGG in the time domain. Since ApEn is a viable single figure of merit, it has the potential to make assessment of aberrant voicing both more concise and objective than the subjective analysis adopted by speech and language therapists (SALTs).

声門上・下圧波形よりみたElectro Glottogramの解析-声の強さによる変化-

The electroglottogram (EGG) has been used to obtain details of vocal fold vibration. Applications of the EGG, however, are limited in use for voice disorders since characteristics of EGG waveforms associated with vocal fold vibrations are still poorly understood. We analysed the EGG waveform characteristics to compare them with simultaneous measurements of supra and subglottic pressure in the normal male subject sustaining the vowel /a/ at constant pitch with different intensity levels. The results are : The periodicities of the consequent frequency are completely coincident among the EGG wave, supra and subglottic pressure waveforms at different intensity levels. With regard to the amplitude variations of the EGG waveform in the vocal cycle, the increasing amplitude corresponded with a rapid increase of subglottic pressure and a decrease of supraglottic pressure which is indicative of the closing phase of the vocal folds. The gradual fall of amplitude associated with the parting of the vocal folds corresponded with an increase of supraglottic pressure from negative values and maintenance of negative subglottic pressure. The negative flatter portion of EGG wave corresponding to the opened phase exhibited higher positive supra glottal pressure and lower pressure of the subglottic even at different sound pressure levels. When increasing the intensity during constant pitch phonation, the values of the contact quotient and contact speed index decreased, and the contact closing slope became steeper.These findings reveal the tendency of increasing vocal tension following louder vocalization. Simultaneous measurement of EGG waveforms, and supraglottic and subglottic pressures might provide useful and detailed information for understanding EGG waveforms, laryngeal dysfunction and/or research for voice disorders.

音声外科の現状と将来・検査，手術，周辺領域編 Ｅｌｅｃｔｒｏｇｌｏｔｔｏｇｒａｐｈｙ （ＥＧＧ）

The electroglottogram (EGG) has been used to measure details of vocal fold vibratory cycles for more than two decades. EGG offers advantages not only for research but also in clinical situations, as it is the most non-invasive technique for subjects and can be performed relatively easily, without requiring any expensive apparatus. It is not uncommon in Europe and the United States for EGG to be used in the clinic for routine examinations of pathological vibrations of the vocal fold.This article covers a variety of aspects relating to EGG including the basic operating principles, the apparatus arrangement, what the EGG waveform actually represents, the validity of the wavef orm, and interpretation of the idiealized wavef orm. In addition, the usefulness of EGG as a technique to measure vibratory cycles both for physiological and pathological vocal folds, objective and visible recordings and biofeedback in voice therapy are described.

歌声声区変換機構の空気力学的, 音響学的検討

Aerodynamic and acoustic characteristics of vocal registers were studied in profressional and non-professional singers. The air flow rate, sound intensity level and fundamental frequency were measured using SH-01 for the speech and singing voices. The rate and magnitude of vibrato were extracted from the singing voices, and an electroglottogram (EGG) was simultaneously recorded.The results were as follows : 1. In the singing mode of a professional soprano singer, the register change from “Chest” to “Mid” occurred at 350 Hz.In “Mid” register, the flow rate increased significantly even though the intensity level did not change remarkably. In the speech mode of the singers and in the singing mode of non-professional singers, the flow rate did not increase so much.2. The estimated open quotient increased when the vocal register changed from “Chest” to “Mid”. At the register changing point, the vibrato tended to be suppressed. Vibrato magnitude was significantly larger in “Mid” register than in “Chest”. There was no significant difference in vibrato rate between the two vocal registers, although it was slightly slower in “Mid” register than in “Chest”. These results suggest that the laryngeal adjustment changes so as to increase the flow rate in “Mid” register, and the change affects vibrato magnitude significantly, but not the vibrato rate.

Clinical Use of the Laryngograph and the Electroglottogram (EGG) with Voice-Disordered Patients

Clinical Use of the Laryngograph and the Electroglottogram (EGG) with Voice-Disordered Patients

Electroglottography and Vocal Fold Physiology

The electroglottogram (EGG) is known to be related to vocal fold motion. A major hypothesis undergoing examination in several research centers is that the EGG is related to the area of contact of the vocal folds. This hypothesis is difficult to substantiate with direct measurements using human subjects. However, other supporting evidence can be offered. For this study we made measurements from synchronized ultra high-speed laryngeal films and from EGG waveforms collected from subjects with normal larynges and patients with vocal disorders. We compare certain features of the EGG waveform to (a) the instant of the opening of the glottis, (b) the instant of the closing of the glottis, and (c) the instant of the maximum opening of the glottis. In addition, we compare both the open quotient and the relative average perturbation measured from the glottal area to that estimated from the EGG. All of these comparisons indicate that vocal fold vibratory characteristics are reflected by features of the EGG waveform. This makes the EGG useful for speech analysis and synthesis as well as for modeling laryngeal behavior. The limitations of the EGG are discussed.

Quality of speech produced by analysis-synthesis

We review factors that have affected the synthesis of high-quality speech by analysis-synthesis. The influence of a selected subset of these factors on the quality of synthesized speech was evaluated through listener preference judgements by comparing natural speech to the synthetic speech of two synthesizers: linear prediction coding (LPC) and formant. Several synthesizer excitation waveforms were considered. These waveforms included critical parameters that replicated selected glottal timing events, e.g., the instants of glottal closure and glottal opening. In addition, identifying voiced/unvoiced/mixed excitation and silent intervals in the speech waveform and measuring the fundamental frequency of voicing contributed to the synthesis of high-quality speech. A two-channel approach to speech analysis is recommended to aid the automatic processing of speech, where one channel is the conventional acoustic signal, while the other channel is the electroglottogram (EGG).

Simultaneous modeling of EGG, PGG, and glottal flow

For obtaining insight into basic aspects of voice quality, an adequate parametrization of the voice source is mandatory. Theoretical studies have shown that changes of the glottal geometry in the direction of flow are an essential prerequisite for self-oscillation of the vocal folds. Thus it is attractive to use stylized glottal shapes as a basis for voice source parametrization, and try to extract the geometry parameters (semi-) automatically from indirect measurements like the electroglottogram (EGG) and photoglottogram (PGG). Titze [J. Acoust. Soc. Am. 75, 570–580 (1984)] presented a model with which he simulated simultaneous measurements of PGG and EGG. It is thought that EGG and PGG are not sufficient for inferring all relevant aspects of glottal geometry. In this paper, it is shown that glottal flow supplies additional information that can be used to impose extra restrictions on the model parameters. Simulations show that when simultaneously modeling EGG, PGG, and glottal flow, it is crucial to assume that the opening of the vocal folds occurs more gently than the closing. Implications of this finding for the description of vocal fold movements in modeling EGG and PGG are discussed.

A model for vocal fold vibratory motion, contact area, and the electroglottogram.

The electroglottogram (EGG) has been conjectured to be related to the area of contact between the vocal folds. This hypothesis has been substantiated only partially via direct and indirect observations. In this paper, a simple model of vocal fold vibratory motion is used to estimate the vocal fold contact area as a function of time. This model employs a limited number of vocal fold vibratory features extracted from ultra high-speed laryngeal films. These characteristics include the opening and closing vocal fold angles and the lag (phase difference) between the upper and lower vocal fold margins. The electroglottogram is simulated using the contact area, and the EGG waveforms are compared to measured EGGs for normal male voices producing both modal and pulse register tones. The model also predicts EGG waveforms for vocal fold vibration associated with a nodule or polyp.