Glottal Parameters Research Articles

Phonation threshold pressure and the elastic shear modulus: Comparison of two-mass model calculations with experiments

Ishizaka and Flanagan's classic two-mass model of vocal fold motion is applied to small oscillations where the equations become linear and the aerodynamic driving force is described by an effective stiffness. The solution of these equations includes an analytic formula for the two eigenfrequencies; this shows that conjugate imaginary parts of the frequencies emerge beyond eigenvalue synchronization and that one of the imaginary parts becomes zero at a pressure signaling the instability associated with the onset of threshold. Using recent measurements by Fulcher et al. of intraglottal pressure distributions [J. Acoust. Soc. Am. 129, 1548-1553 (2011).] to inform the behavior of the entrance loss coefficients, an analytic formula for threshold pressure is derived. It fits most of the measurements Chan and Titze reported for their 2006 physical model of the vocal fold mucosa. Two sectors of the mass-stiffness parameter space are used to produce these fits. One is based on a rescaling of the typical glottal parameters of the original Ishizaka and Flanagan work. The second requires setting two of the spring constants equal and should be closer to the experimental conditions. In both cases, values of the elastic shear modulus are calculated from the spring constants.

Auto-crosslinked hyaluronan gel injections in phonosurgery

Objectives To evaluate the clinical performance of an auto-crosslinked gel obtained from hyaluronic acid (ACP-based gel) as an anti-adhesive agent and/or augmentative agent in vocal cord surgery for the treatment of vocal fold (VF) atrophy, sulcus vocalis, and postsurgery scarring as well as its tolerability at short- and long-term follow-up. Study Design This was a prospective multicenter trial conducted between 2007 and 2009. Setting Academic center. Subjects and Methods Inclusion criteria were patients with glottic gap due to previous endoscopic phonosurgery, VF scars, vocal cord atrophy, and sulcus vocalis. Forty patients who underwent endoscopic injection of hyaluronic acid under general anesthesia were enrolled. Two different injections sites were used: the thyroarytenoid muscle in cases of glottic gap for augmentative purposes, and the lamina propria for treatment of scars and sulcus vocalis. A voice-evaluation protocol was performed before surgery, at the first follow-up visit (3 mo), and at the final follow-up (12 mo). Results Follow-up data at three months were available for 38 patients, while data at 12 months follow-up were available for 27 patients. No side effects, hematoma, or infection and allergic reactions were reported in either the perioperative or postoperative period. Patients had statistically significant improvement in voice parameters compared with the baseline data at the first follow-up visit and at the 12-month follow-up. Conclusion ACP-based gel seems to be a new tool in the challenging treatment of VF scarring, functioning as both an anti-adhesive product and an augmentation agent. Improvements in all glottal parameters and in both objective and subjective evaluation of voice performance were observed.

Exploring the Effect of Differences in the Acoustic Correlates of Adults' and Children's Speech in the Context of Automatic Speech Recognition

This work explores the effect of mismatches between adults' and children's speech due to differences in various acoustic correlates on the automatic speech recognition performance under mismatched conditions. The different correlates studied in this work include the pitch, the speaking rate, the glottal parameters (open quotient, return quotient, and speech quotient), and the formant frequencies. An effort is made to quantify the effect of these correlates by explicitly normalizing each of them using the already existing techniques available in literature. Our initial study done on a connected digit recognition task shows that among these parameters only the formant frequencies, the pitch, and the speaking rate affect the automatic speech recognition performance. Significant improvements are obtained in the performance with normalization of these three parameters. With combined normalization of the pitch, the speaking rate, and the formant frequencies, 80% and 70% relative improvements are obtained over the baseline for children's speech and adults' speech recognition under mismatched conditions.

Speaker verification system using acoustic data and non-acoustic data

A method and system for speech characterization. One embodiment includes a method for speaker verification which includes collecting data from a speaker, wherein the data comprises acoustic data and non-acoustic data. The data is used to generate a template that includes a first set of “template” parameters. The method further includes receiving a real-time identity claim from a claimant, and using acoustic data and non-acoustic data from the identity claim to generate a second set of parameters. The method further includes comparing the first set of parameters to the set of parameters to determine whether the claimant is the speaker. The first set of parameters and the second set of parameters include at least one purely non-acoustic parameter, including a non-acoustic glottal shape parameter derived from averaging multiple glottal cycle waveforms.

Voice source parameter measurement based on multi-scale analysis of electroglottographic signal

This paper deals with glottal parameter measurement from electroglottographic signal (EGG). The proposed approach is based on GCI and GOI determined by the multi-scale analysis of the EGG signal. Wavelet transform of EGG signal is done with a quadratic spline function. Wavelet coefficients calculated on different dyadic scales, show modulus maxima at localized discontinuities of the EGG signal. The detected maxima and minima correspond to the so-called GOIs and GCIs. To improve the GCI and GOI localization precision, the product of wavelet transform coefficients of three successive dyadic scales, called multi-scale product (MP), is operated. This process enhances edges and reduces noise and spurious peaks. Applying the cubic root amplitude on the multi-scale product improves the detection of weak GOI maximum and avoids the GCI misses. Applied on the Keele University database, the method brings about a good detection of GCI and GOI. Based on the GCI and GOI, voicing classification, pitch frequency and open quotient measurements are processed. The proposed voicing classification approach is evaluated with additive noise. For clean signal the performance is of 96.4%, and at SNR level of 5 dB, the performance is of 93%. For the fundamental frequency and the open quotient measurement, the comparison of the MP with the DEGG, Howard (3/7), the threshold (35% and 50%), and the DECOM methods show that this new proposed approach is similar to the major methods with an improvement displayed by its lowest deviation.

Quantitative microlaryngoscopic measurements of vocal fold polyps, glottal gap and their relation to vocal function

The purpose of this study was to quantify the size of vocal fold polyps and to investigate the relationship between the glottal gap and parameters of acoustic voice analysis and phonetography. Eighty-one microlaryngoscopic images and digital recordings of voices (acoustic analysis and phonetogram) acquired from the patients with vocal fold polyps (VFPs) were employed in this study. Vocal fold (VF) images were collected during routine direct microlaryngoscopy using Moller-Wedel Universa 300 surgical microscope, 3-CCD Elmo 768 x 576-pixel color video camera and a 300 W Xenon light source. Acoustic voice analysis and phonetography were established using Dr. Speech (Tiger Electronics Inc.) software. Microlaryngoscopic images were processed by original software created by ELINTA and displayed on a monitor. The relative lengths and widths of vocal fold polyps as well as percentage area of VFP were calculated. The Pearson's correlation was applied to reveal the correlation between VFP dimensions and acoustic voice parameters. There were no statistically significant differences between the dimensions of left and right vocal folds and VFPs. Statistically significant slight to mild correlations between measured dimensions of VFP acoustic and phonetogram parameters were revealed, with HNR and phonetogram area showing the strongest correlation to the size of VFPs. The results of our study confirm that quantitative microlaryngoscopic measurements of vocal fold polyp and glottal gap dimensions may be a useful tool for objective assessment of glottic incompetence and voice impairment.

Electroglottographic Measures Based on GCI and GOI Detection Using Multiscale Product

This paper deals with glottal parameter estimation such as local pitch and open quotient from electroglottographic signal (EGG). This estimation is based on glottal closing instants and glottal opening instants determined by a multi-scale product of this signal. Wavelet transform of EGG signal is made with a quadratic spline function. Wavelet coefficients calculated on different dyadic scales, show modulus maxima at localized discontinuities of EGG signal. The detected maxima and minima correspond to the glottal opening and closing instants called GOIs and GCIs. To improve the estimate precision, we operate the multi-scale product of wavelet transform coefficients of three successive dyadic scales. This processing enhances edge detection. A Multi-scale product is a nonlinear combination of successive scales; it reduces noise and spurious peaks. We apply cubic root amplitude on the product to improve the representation of weak amplitudes. The method has a good representation of GCI and a best detection of GOI. The method was tested on the Keele University database; it is effective and robust in multiple cases even for a typical signal showing undetermined GOIs and multiple peaks at GCIs. Finally precise measurement of these instants allows accurate estimation of prosodic parameters as local pitch and open quotient.

Dynamic MRI of Larynx and Vocal Fold Vibrations in Normal Phonation

Dynamic magnetic resonance imaging (MRI) of the larynx and vocal folds during phonation was used for measuring the vertical laryngeal movements and the glottal angle of the vocal folds opening and closing in dynamic phase. The data used in this analysis were taken on 10 healthy volunteers during maximal inspiration and the prolonged phonation of the vowels [i] (as in key), [a] (as in car), [u] (as in loop), and the consonant [sh] (as in ship). The results of our MRI data have demonstrated the difference of the vocal folds movement in relation to the vowel and consonant sounds, with a large glottal opening for [sh] and a narrow opening for [i] and [u], and the difference of the laryngeal position in relation to the vowels, with [a] and [u] having a lower larynx position than [i]. Imaging the larynx's positions and the vocal folds' vibrations is possible using dynamic MRI. This technique permits measurements of laryngeal structures and glottal parameters in dynamic function with multiplanar high-resolution imaging. Analysis of laryngeal activity and vocal folds' vibration may be helpful for the evaluation of the phonation function and for the understanding of the physiology of vocal production and voice modulation.

Robust Glottal Source Estimation Based on Joint Source-Filter Model Optimization

This paper describes a robust glottal source estimation method based on a joint source-filter separation technique. In this method, the Liljencrants–Fant (LF) model, which models the glottal flow derivative, is integrated into a time-varying ARX speech production model. These two models are estimated in a joint optimization procedure, in which a Kalman filtering process is embedded for adaptively identifying the vocal tract parameters. Since the formulated joint estimation problem is a multiparameter nonlinear optimization procedure, we separate the optimization procedure into two passes. The first pass initializes the glottal source and vocal tract models by solving a quasi-convex approximate optimization problem. Having robust initial values, the joint estimation procedure determines the accuracy of model estimation implemented with a trust-region descent optimization algorithm. Experiments with synthetic and real voice signals show that the proposed method is a robust glottal source parameter estimation method with a high degree of accuracy.

Vowel Effect on Glottal Parameters and the Magnitude of Jaw Opening

This study investigated the relationship among the magnitude of jaw opening, intrinsic fundamental frequency (F0), and glottal parameters in natural speech. Acoustic, jaw opening, and electroglottographic (EGG) signals were simultaneously recorded. The subjects were 10 healthy men with New Zealand English as their native language. Subjects were asked to repeat a standard nonemphasized sentence in which one of the target vowels (/a/, /e/, /i/, /o/, and /u/) was embedded in various contexts. The glottal parameters F0, open quotient (OQ), and speed quotient (SQ) were measured from the EGG signal. Results of a series of one-way repeated-measures analyses of variance (ANOVA) showed a significant vowel effect on the magnitude of jaw opening [F(4, 24) = 25.512, P < .001], F0 [F(4, 28) = 45.415, P < .001] and speed quotient [F(4, 28) = 5.233, P = .003], but not on the open quotient [F(4, 28) = 0.501, P = .735]. The magnitude of jaw opening was found to be inversely related with F0 (r = -0.624, n = 25, P = .0009). These findings showed that the magnitude of jaw opening was related to F0 and that jaw opening might be a control signal for simulation of long-term F0 variation to achieve a higher degree of naturalness in artificial voice.

Comparison between automatic and manual inverse filtering procedures for healthy female voices

Indirect observations of the vocal fold vibrations can be made from the glottal airflow waveform using the non-invasive technique of inverse filtering the oral airflow. The aim was to evaluate the automatic inverse filtering program ?Inverse?, that is, a pitch-asynchronous method based on linear prediction analysis. Oral airflow was recorded with a differential pressure transducer in a Rothenberg mask. Intraoral pressure, the electroglottographic (EGG) and acoustic signals were recorded simultaneously. Seventeen healthy women produced [ba:pa:pa:pa:p] in normal, soft and loud voice. Comparisons were made between results from inverse filtering performed using a manual procedure (Glottal Enterprises System) and the automatic program ?Inverse?. The glottal airflow waveform parameters peak flow, minimum flow, peak-to-peak flow, and the maximum negative flow derivative were extracted. High agreement between the two inverse filtering procedures was reflected by high correlation coefficients for each of the airflow parameters (r0.96). The absolute values of the parameters were generally lower for the automatic procedure (1.2-7.7%). This was thought to be due to the different low pass filter characteristics and the different number of anti-resonances used in the two methods. Inverse filtering requires careful control of the recording, and the results must be interpreted thoroughly also after automatic analysis. With those considerations, we conclude that the automatic program ?Inverse? can be used in clinical settings.

Reliability of computerized measurements of glottal insufficiency

The aim of this study was to evaluate the reliability of computerized measurements of glottal parameters from videostroboscopic examinations. Ten patients with glottal insufficiency of different etiology received collagen injections. Measurements of vocal fold length, glottal area and amplitude of the vocal fold vibrations were obtained before and after injection. Repeat measurements from 43% of randomly chosen frames showed a high consistency for the parameters vocal fold length (r=0.984) minimum glottal area (r=0.967), and glottal area variation (r=0.987). Consistency of vibration amplitude was lower (r=0.795). This study shows that computerized measurements are suitable tools in the evaluation of vocal fold injection treatment for glottal insufficiency.

Glottal source parameter estimation by comparison of measured signals with simulated signals

Oral flow, electroglottographic (EGG), and photoglottographic (PGG) signals were simultaneously digitized from a single subject phonating sustained vowels. Analogous simulated signals—oral flow, vocal fold contact area, and glottal area, respectively—were produced by a driven, kinematic glottal source model coupled to a wave-reflection-type vocal tract. The vocal tract area function used in the simulation was estimated from magnetic resonance imaging (MRI) data previously published for the subject. This essentially removed the vocal tract as a confounding factor in the analysis. The measured and simulated signals were compared and an attempt was made to adjust model parameters so that the least-squared differences between the signals were minimized. The model parameters, which included subglottal pressure, vocal fold adduction, vocal fold convergence, and fundamental frequency were observed to be estimates for the glottal configuration and control parameters used by the subject.

Variation of subglottal pressure during sentence production: Effect on glottal source amplitude and spectrum.

With the goal of synthesizing natural‐sounding speech based on higher‐level parameters, variations in subglottal pressure for sentences having different stress patterns have been studied. A Rothenberg mask was used to collect oral pressure and airflow signals from several subjects producing reiterant speech. Acoustic sound pressure was also recorded, and sound pressure levels (SPLs) for both reiterant and natural utterances were compared to verify the suitability of reiterant speech for the task. Subglottal pressure Ps was inferred from oral pressure measured during stop consonant closure of reiterant speech, average glottal flow Ug was estimated from the low‐pass‐filtered airflow signals, and average glottal area Ag was calculated using Ps and Ug. Glottal source amplitude and spectral tilt were estimated from the speech waveform. Preliminary analysis shows that accented syllables are marked by an increase in Ps of about 50% relative to the weakest unaccented syllables, an increase in SPL of 10 to 15 dB, and some increase in Ag. A model for estimating glottal parameters during these utterances has been developed. Attempts to synthesize sentences based on this model, by including Ag and Ps as control parameters, are described. [Work supported by NIH grants DC00075 and MH52358.]

Glottal impedance based on a finite element analysis of two-dimensional unsteady viscous flow in a static glottis

Unsteady viscous flows in various static models of the glottis are numerically simulated using a finite-element method, and parameters of the electrically equivalent impedances in the models are determined. Different shapes of the static models, which are obtained by varying the angle and diameter of the glottis, produce flow patterns quite different from each other. Really complicated flow patterns have been obtained with the help of appropriate preprocessing/postprocessing software. The equivalent glottal impedance parameters are evaluated. The equivalent resistance values are compared with those derived by previously proposed formulas, and the equivalent inductance values are compared with the analytic solution derived from the Navier-Stokes equations. The present results closely approximate real flow measurements already reported, thus indicating that the numerical method approximates the real phenomena and is therefore useful for the analysis of vocal sources. >

A study of the variation of glottal pulse shape with fundamental frequency by inverse filtering of the speech wave

The acoustics of speech production is based on the concept of a source and a filter function. In current models the source of voiced sounds is represented by a quasiperiodic succession of pulses of air emitted through the glottis, as the vocal cords open and close, and the filter function is assumed to be linear and short‐time invariant. The source term or the acoustic excitation produced by the larynx is subject to variation in speech produced by a natural speaker. The analysis described here forms part of an investigation into variation of the shape of the glottal volume velocity waveform as a function of fundamental frequency. The deconvolution of the speech wave, i.e., separation of the glottal pulse signal from the vocal tract impulse response, is done by inverse filtering the speech signal using a filter derived in the closed phase of the glottal cycle. Linear predictive covariance analysis is used in estimating the inverse filter coefficients. A linear relationship between the glottal parameters, open phase, opening duration, and closing duration with time period is shown. A model is then proposed for the variation of these glottal parameters with fundamental frequency.

Predicting Voice Quality of Deaf Speakers on the Basis of Glottal Characteristics

Twenty profoundly deaf and 5 normal-hearing subjects produced 225 sustained vowels/a, i, u/at different pitch levels and 75 phonetically balanced sentences, while vocal fold vibration was recorded through an electrolaryngograph (ELG). The utterances recorded on audio tape were judged by 10 experienced listeners on general voice quality, breathiness, hoarseness, and laryngeal strain on a 5-point scale. Seven parameters describing time-domain characteristics of the ELG-signal were extracted online by a special purpose computer system. Measurements were made over 500 consecutive vibratory cycles (10-cycle window), yielding a mean and standard deviation for each parameter per utterance. All data were submitted to analysis of variance and multiple regression analyses. Multiple correlations between glottal parameters and judged voice deviations varied between .46 and .70 indicating that overall prediction cannot reliably be based on these parameters, although severe cases of deaf voice deviations may be detectable.

Speech analysis and synthesis using a vocal tract/cord model

The use of our vocal cord and tract model [Schroeter and Sondhi, J. Acoust. Soc. Am. Suppl. 1 78, S6 (1985)] for speech coding at bit rates below 4.8 kb/s is being considered. Earlier work [Flanagan et al., J. Acoust. Soc. Am. 68, 780–791 (1980)] reported on applying an unconstrained optimization method for jointly finding the best vocal tract and glottal parameters directly from the speech signal (one‐stage optimization). This method has been extended by optimizing tract and glottal parameters sequentially (two‐stage optimization). In a first stage, a search was made for the parameters of an inverse (tract) filter that give the best match between the inverse filtered speech and the output of the vocal cord model for a given set of glottal parameters. In a second stage, the parameters of the cord model were optimized for a given set of tract parameters so that the synthesized speech matches the original speech as closely as possible. This method has the advantage of separating the source and tract into different optimization stages. By doing so, the inherent constraints of the respective models can be easily used to constrain the search space. Compared to the one‐stage optimization, the search required in each stage is over a parameter space of a smaller dimension. Different start‐up procedures for the two‐stage optimization are investigated. Results are compared to those of the one‐stage optimization.

A text to speech synthesizer for the personal computer

A compact and low cost text to speech synthesis unit for the personal computer has been developed. This unit uses an LSI speech synthesizer with formant parameters. The speech synthesis method used is based on speech synthesis by rule using the CV, VC speech segments compilation method and the glottal pole formant model. In order to obtain high quality, the analysis-synthesis technique has been introduced. The glottal pole and formant parameters for CV, VC segments are extracted by a kind of analysis by synthesis technique. A Japanese text to speech synthesis system has been developed using these techniques. Intelligibility tests for well known Japanese words indicated an about 1% error rate.

Estimation of articulatory motion by a model matching method

First, an effective method to describe the position of the articulatory organs is presented. The method relies on the statistical analysis of real data. The vocal tract shape is specified effectively by five articulatory parameters, the angle of jaw opening, two principal components for the various tongue shapes, lip parameter, and glottal parameter. Next, this articulatory model is used to estimate articulatory motion from speech waves. The articulatory parameters are estimated by minimizing the spectral error with some constraints. This is a nonlinear optimization problem and is solved by an iterative procedure. The power spectrum of the speech wave is composed of the vocal tract transfer function and the glottal wave characteristic. The spectral shape of the vocal tract transfer function is separated in such a way that the formant structure is preserved. Combined with a procedure to adjust the mean vocal tract length for each speaker, this method is very successful in estimating the articulatory parameters from vowel sounds. [Work supported by Ministry of Education Grant‐in‐Aid for Scientific Research No. 239005]