Standardized laryngeal videostroboscopic rating: differences between untrained and trained male and female subjects, and effects of varying sound intensity, fundamental frequency, and age

Effects of Speech Characteristics on Electroglottographic and Instrumental Acoustic Voice Analysis Metrics in Women With Structural Dysphonia Before and After Treatment

PURPOSE

Literature suggests a dependency of the acoustic metrics, smoothed cepstral peak prominence (CPPS) and harmonics-to-noise ratio (HNR), on human voice loudness and fundamental frequency (F0). Even though this has been explained with different oscillatory patterns of the vocal folds, so far, it has not been specifically investigated. In the present work, the influence of three elicitation levels, calibrated sound pressure level (SPL), F0 and vowel on the electroglottographic (EGG) and time-differentiated EGG (dEGG) metrics hybrid open quotient (OQ), dEGG OQ and peak dEGG, as well as on the acoustic metrics CPPS and HNR, was examined, and their suitability for voice assessment was evaluated.

METHOD

In a retrospective study, 29 women with a mean age of 25 years (± 8.9, range: 18-53) diagnosed with structural vocal fold pathologies were examined before and after voice therapy or phonosurgery. Both acoustic and EGG signals were recorded simultaneously during the phonation of the sustained vowels /ɑ/, /i/, and /u/ at three elicited levels of loudness (soft/comfortable/loud) and unconstrained F0 conditions.

RESULTS

A linear mixed-model analysis showed a significant effect of elicitation effort levels on peak dEGG, HNR, and CPPS (all p < .01). Calibrated SPL significantly influenced HNR and CPPS (both p < .01). Furthermore, F0 had a significant effect on peak dEGG and CPPS (p < .0001). All metrics showed significant changes with regard to vowel (all p < .05). However, the treatment had no effect on the examined metrics, regardless of the treatment type (surgery vs. voice therapy).

CONCLUSIONS

The value of the investigated metrics for voice assessment purposes when sampled without sufficient control of SPL and F0 is limited, in that they are significantly influenced by the phonatory context, be it speech or elicited sustained vowels. Future studies should explore the diagnostic value of new data collation approaches such as voice mapping, which take SPL and F0 effects into account.

Differences and Reliability of Linear and Nonlinear Acoustic Measures as a Function of Vocal Intensity in Individuals With Voice Disorders

PURPOSE

Linear acoustic indices are significantly influenced by speaking voice intensity. The main aim of this work was to compare acoustic measures based on linear and nonlinear models in different speaking voice intensity levels and to analyze the reliability of those measures in different intensity levels in subjects with voice disorders.

METHODS

435 samples from subjects (314 women, 121 men with a mean age of 41.07 ± 13.73) diagnosed with various voice disorders were used. In total, 17 acoustic measures were derived from the vowel /ɛ/ sustained at three intensity levels (soft, comfortable, and loud). Five were linear (standard deviation of the fundamental frequency (f0), jitter, shimmer, harmonics-to-noise ratio (HNR) and smoothed cepstral peak prominence (CPPS)), and twelve were nonlinear measures, namely correlation dimension (D2), correlation entropy (H2), first minimum of the mutual information function (FMMI), relative entropy (ENTR-R), largest Lyapunov exponent (Lyap), determinism (DET), transitivity, mean diagonal line length (Lmed), Shannon entropy (ENTR-S), mean length of vertical structures, also known as trapping time (TT), laminarity (LAM) and recurrence period density entropy (RPDE). Differences between speaking voice intensity levels were assessed by Friedman's test and Nemenyi as posthoc test. Intraclass correlation coefficient was used to investigate if each acoustic measure remains in agreement (reliability) between different voice intensity levels.

RESULTS

There were significant differences in all acoustic measures about vocal intensity level (P < 0.001). Intraclass correlation coefficient was very good for HNR (>0.61) and good for Lyap, DET, ENTR-S, Lmed, RPDE, and TT (0.41-0.60).

CONCLUSIONS

All acoustic measures varied as a function of vocal intensity in voice disordered adults, while this relation was different for linear and nonlinear measures. Only the measures HNR, Lyap, DET, ENTR-S, Lmed, RPDE and TT had an acceptable reliability between different voice intensity levels. Therefore, patient`s voice SPL should be controlled or indicated during acoustic vocal assessment.

Acoustic Measures of Voice and Physiologic Measures of Autonomic Arousal During Speech as a Function of Cognitive Load in Older Adults

OBJECTIVES/HYPOTHESIS

The purpose of this study was to determine the relationships among cognitive loading, autonomic arousal, and acoustic measures of voice in healthy older adults.

STUDY DESIGN

Prospective and observational.

METHODS

Twelve healthy older adults (six females) produced a sentence containing an embedded Stroop task in each of two cognitive load conditions: congruent and incongruent. Three physiologic measures of autonomic arousal (pulse volume amplitude, pulse period, and skin conductance response amplitude) and four acoustic measures of voice (cepstral peak prominence, low-to-high spectral energy ratio, fundamental frequency, and sound pressure level) were analyzed in each cognitive load condition.

RESULTS

A logistic regression model was used to predict the cognitive load condition using participant as a categorical predictor and the four acoustic measures and three autonomic measures as continuous predictors. Skin conductance response amplitude and pulse volume amplitude were both predictive of cognitive load; however, no acoustic measures of voice were statistically significant predictors of cognitive load for older adults.

CONCLUSIONS

These findings support the idea that increased cognitive load is associated with increased autonomic nervous system activity in older adults. The lack of changes in acoustic measures of voice with increased cognitive load may result from age-related changes in vocal quality and speech subsystems.

Aged voice: does advancing age generate different impacts?

PURPOSE

To verify if there are differences in the vocal aspects of older people from three different age groups with presbyphonia diagnosis.

METHODS

Sixty older adults joined this study. They were both female and male, with an age range from 60 to 90 years old (average: 72.3) and with presbyphonia diagnosis established after otolaryngology evaluation. From their voice recordings, it was possible to make the acoustic and auditory-perceptual analysis. The data collected was compared through statistical tests considering the division of the participants into the following groups: 60-70 years old, 71-80 years old, and 81-90 years old.

RESULTS

Even though the older people from all of the three groups have presented deviation in multiple vocal aspects such as instability and vocal noise in low frequencies, those with more than 80 years old have presented a higher deviation of the general grade of dysphonia, roughness, breathiness, and pitch. In this group, it was also observed higher deviations in jitter, shimmer, vocal breaks, and the GNE measure on the edge of normality. All the differences were statistically significant. The majority of the older participants from that group presented even a deviation in the phonatory deviation diagram and frequency break.

CONCLUSION

Various acoustic and auditory-perceptual aspects had a higher deviation in the older adults over 80 years old, which reinforces the need to consider those specificities in the evaluation of the vocal aging impacts and also in the development of actions to minimize vocal declination.

A Portable Smartphone-Based Laryngoscope System for High-Speed Vocal Cord Imaging of Patients With Throat Disorders: Instrument Validation Study

Background

Currently, high-speed digital imaging (HSDI), especially endoscopic HSDI, is routinely used for the diagnosis of vocal cord disorders. However, endoscopic HSDI devices are usually large and costly, which limits access to patients in underdeveloped countries and in regions with inadequate medical infrastructure. Modern smartphones have sufficient functionality to process the complex calculations that are required for processing high-resolution images and videos with a high frame rate. Recently, several attempts have been made to integrate medical endoscopes with smartphones to make them more accessible to people in underdeveloped countries.

Objective

This study aims to develop a smartphone adaptor for endoscopes, which enables smartphone-based vocal cord imaging, to demonstrate the feasibility of performing high-speed vocal cord imaging via the high-speed imaging functions of a high-performance smartphone camera, and to determine the acceptability of the smartphone-based high-speed vocal cord imaging system for clinical applications in developing countries.

Methods

A customized smartphone adaptor optical relay was designed for clinical endoscopy using selective laser melting–based 3D printing. A standard laryngoscope was attached to the smartphone adaptor to acquire high-speed vocal cord endoscopic images. Only existing basic functions of the smartphone camera were used for HSDI of the vocal cords. Extracted still frames were observed for qualitative glottal volume and shape. For image processing, segmented glottal and vocal cord areas were calculated from whole HSDI frames to characterize the amplitude of the vibrations on each side of the glottis, including the frequency, edge length, glottal areas, base cord, and lateral phase differences over the acquisition time. The device was incorporated into a preclinical videokymography diagnosis routine to compare functionality.

Results

Smartphone-based HSDI with the smartphone-endoscope adaptor could achieve 940 frames per second and a resolution of 1280 by 720 frames, which corresponds to the detection of 3 to 8 frames per vocal cycle at double the spatial resolution of existing devices. The device was used to image the vocal cords of 4 volunteers: 1 healthy individual and 3 patients with vocal cord paralysis, chronic laryngitis, or vocal cord polyps. The resultant image stacks were sufficient for most diagnostic purposes. The cost of the device including the smartphone was lower than that of existing HSDI devices. The image processing and analytics demonstrated the successful calculation of relevant diagnostic variables from the acquired images. Patients with vocal pathologies were easily differentiable in the quantitative data.

Conclusions

A smartphone-based HSDI endoscope system can function as a point-of-care clinical diagnostic device. The resulting analysis is of higher quality than that accessible by videostroboscopy and promises comparable quality and greater accessibility than HSDI. In particular, this system is suitable for use as an accessible diagnostic tool in underdeveloped areas with inadequate medical service infrastructure.

Integrative Insights into the Myoelastic-Aerodynamic Theory and Acoustics of Phonation. Scientific Tribute to Donald G. Miller

In this tribute article to D.G. Miller, we review some historical and recent contributions to understanding the myoelastic-aerodynamic (MEAD) theory of phonation and the related acoustic phenomena in subglottal and vocal tract. At the time of the formulation of MEAD by van den Berg in late 1950s, it was assumed that vocal fold oscillations are self-sustained thanks to increased subglottal pressure pushing the glottis to open and decreased subglottal pressure allowing the glottis to close. In vivo measurements of subglottal pressures during phonation invalidated these assumptions, however, and showed that at low fundamental frequencies subglottal pressure rather tends to reach a maximum value at the beginning of glottal closure and then exhibits damped oscillations. These events can be interpreted as transient acoustic resonance phenomena in the subglottal tract that are triggered by glottal closure. They are analogous to the transient acoustic phenomena seen in the vocal tract. Rather than subglottal pressure oscillations, a more efficient mechanism of transfer of aerodynamic energy to the vocal fold vibrations has been identified in the vertical phase differences (mucosal waves) making the glottal shape more convergent during glottis opening than during glottis closing. Along with other discoveries, these findings form the basis of our current understanding of MEAD.

Vocal fold nodules: A disorder of phonation organs or auditory feedback?

OBJECTIVE

Increasing evidence supports that auditory feedback of one's own voice closely relates to real-time adjustments of vocal control. Previous studies highlighted that the low-frequency modulations of below 3 Hz (LFM) embedded in vocal fundamental frequency (F0) showed a reflex-like response to altered auditory inputs. However, the auditory feedback control of different vocal disorders remains unclear.

DESIGN

A cross-sectional, case-controlled study.

SETTING

A tertiary medical centre.

PARTICIPANTS

Sustained vocalisations of vowel/a/ from adult healthy controls and patients with vocal fold nodules, vocal fold polyps and vocal fold cysts, respectively. The vocalisations were made at a comfortable pitch and at the intensity of 70 ~ 80 dBC under the following four auditory conditions: natural hearing, 90-dBC speech noise, 10-dBC enhanced feedback of self-produced voice and both the noise and voice feedback.

MAIN OUTCOME MEASURES

Power spectral analysis of F0 contour of sustained vowel.

RESULTS

Patients with vocal fold nodules presented with different audio-vocal feedback behaviour and audio-vocal response to speech noise from the other two vocal pathologies of vocal fold polyp and vocal fold cyst as well as the healthy controls (P < .001, one-way ANOVA).

CONCLUSION

The vocal fold nodules may be not only a vocal fold disease but also a disease caused by abnormal audio-vocal feedback. Moreover, the distinct audio-vocal feedback of vocal fold nodules could be revealed by power spectral analysis of vocal fundamental frequencies. Although further investigations are necessary, adjustments of audio-vocal feedback behaviour may provide a new insight and benefit to the treatment of vocal fold nodules in the future.

A Simple Method to Obtain Basic Acoustic Measures From Video Recordings as Subtitles

PURPOSE

Sound pressure level (SPL) and fundamental frequency (fo) are very basic and important measures in the acoustical assessment of voice quality, and their variation influences also the vocal fold vibration characteristics. Most sophisticated laryngeal videostroboscopic systems therefore also measure and display the SPL and fo values directly over the video frames by means of a rather expensive special hardware setup. An alternative simple software-based method is presented here to obtain these measures as video subtitles.

METHOD

The software extracts acoustic data from the video recording, calculates the SPL and fo parameters, and saves their values in a separate subtitle file. To ensure the correct SPL values, the microphone signal is calibrated beforehand with a sound level meter.

RESULTS

The new approach was tested on videokymographic recordings obtained laryngoscopically. The results of SPL and fo values calculated from the videokymographic recording, subtitles creation, and their display are presented.

CONCLUSIONS

This method is useful in integrating the acoustic measures with any kind of video recordings containing audio data when inbuilt hardware means are not available. However, calibration and other technical aspects related to data acquisition and synchronization described in this article should be properly taken care of during the recording.

Sex differences in respiratory function

Men Are from Mars, Women Are from Venus. John Gray used this provocative title for his book to describe the fundamental psychological differences between the sexes. Many other controlled studies and brain scans demonstrate that men and women are physically and mentally different. The purpose of this physiology masterclass is to illustrate how sex-related differences are present in respiratory function and their possible clinical implications.

An overview of sex-related differences in respiratory function and their possible clinical implicationshttp://ow.ly/106m30jqOSW

Acoustic Perturbation Measures Improve with Increasing Vocal Intensity in Individuals With and Without Voice Disorders

OBJECTIVE

In vocally healthy children and adults, speaking voice loudness differences can significantly confound acoustic perturbation measurements. This study examines the effects of voice sound pressure level (SPL) on jitter, shimmer, and harmonics-to-noise ratio (HNR) in adults with voice disorders and a control group with normal vocal status.

STUDY DESIGN

This is a matched case-control study.

METHODS

We assessed 58 adult female voice patients matched according to approximate age and occupation with 58 vocally healthy women. Diagnoses included vocal fold nodules (n = 39, 67.2%), polyps (n = 5, 8.6%), and muscle tension dysphonia (n = 14, 24.1%). All participants sustained the vowel /a/ at soft, comfortable, and loud phonation levels. Acoustic voice SPL, jitter, shimmer, and HNR were computed using Praat. The effects of loudness condition, voice SPL, pathology, differential diagnosis, age, and professional voice use level on acoustic perturbation measures were assessed using linear mixed models and Wilcoxon signed rank tests.

RESULTS

In both patient and normative control groups, increasing voice SPL correlated significantly (P < 0.001) with decreased jitter and shimmer, and increased HNR. Voice pathology and differential diagnosis were not linked to systematically higher jitter and shimmer. HNR levels, however, were statistically higher in the patient group than in the control group at comfortable phonation levels. Professional voice use level had a significant effect (P < 0.05) on jitter, shimmer, and HNR.

CONCLUSIONS

The clinical value of acoustic jitter, shimmer, and HNR may be limited if speaking voice SPL and professional voice use level effects are not controlled for. Future studies are warranted to investigate whether perturbation measures are useful clinical outcome metrics when controlling for these effects.

Reliability of High-speed Videoendoscopic Ratings of Essential Voice Tremor and Adductor Spasmodic Dysphonia

OBJECTIVES

The main objectives of this study were to (1) examine intrarater and inter-rater reliabilities in perceptual ratings of vocal fold vibratory patterns and supraglottic characteristics for essential vocal tremor and adductor spasmodic dysphonia (AdSD) using high-speed videoendoscopy (HSV), and (2) to investigate the specificity of the parameters in differentiating these two voice disorders.

METHODS

HSV recordings of 34 cases diagnosed with essential vocal tremor, AdSD, or AdSD with vocal tremor were evaluated blindly by two voice speech pathologists. The two raters examined all HSV video segments twice across nine supraglottic and vocal fold vibratory characteristics for inter-rater and intrarater reliabilities. A separate consensus rating was then developed, with the results analyzed to explore differentiation.

RESULTS

Raters demonstrated moderate intrarater reliability with mean Spearman's rho correlation coefficients of 0.68 (rater 1) and 0.73 (rater 2). Moderate inter-rater reliability for the two raters was seen across all parameters with a mean Cohen's kappa coefficient of 0.51. Raters showed higher intrarater and inter-rater reliabilities for supraglottic parameters. Only the presence of tremor differentiated between the two voice disorders in cases with a consistent diagnosis.

CONCLUSIONS

The high level of concomitance between vocal tremor and AdSD may affect subjective perceptual analysis of supraglottic and vocal fold vibratory patterns. Results indicate similar global involvement of supraglottic laryngeal structures for both vocal tremor and AdSD.

Impact of topical anesthesia on acoustic characteristics of voice during laryngeal telescopic examination

OBJECTIVE:

The purposes of this study are to investigate the impact of topical anesthetic alone and with concurrent laryngeal telescopic examination on acoustic characteristics of vocal fold function. Comparison with phonation in controlled conditions may imply diagnostic information from the examination.

STUDY DESIGN:

Thirty males evaluated as having a normal voice were included in the study. The subjects were asked to phonate sustained /i/ with a naturally comfortable pitch and loudness in three consecutive experimental sequences as “control condition,” “anesthetic condition,” and “telescopic condition.” Acoustic analysis of fundamental frequency, jitter, shimmer, and harmonic to noise ratio in the three different conditions were executed.

RESULTS:

The mean and standard deviation of Fo in control condition, anesthetic condition, and telescopic condition were 130.1 ± 18.5 Hz, 125.7 ± 19.7 Hz, and 173.2 ± 35.1 Hz, respectively. The telescopic condition showed more negative change than that in control condition and anesthetic condition in other parameters. There was a significant difference ( P < 0.001) between control condition and telescopic condition in all four parameters.

CONCLUSIONS:

This study showed that anesthesia has little effect on voice performance for subjects with a normal voice. On the other hand, the acoustic characteristics changed significantly during telescopic performance. When doing interpretation of acoustic data, the abnormality of the acoustic characteristics might be the result of the procedures and not reflect vocal pathology. Laryngeal variations due to manipulation of telescope should be ruled out.

A Preliminary Quantitative Comparison of Vibratory Amplitude Using Rigid and Flexible Stroboscopic Assessment

STUDY OBJECTIVE

The purpose of this study was to establish preliminary, quantitative data on amplitude of vibration during stroboscopic assessment in healthy speakers with normal voice characteristics. Amplitude of vocal fold vibration is a core physiological parameter used in diagnosing voice disorders, yet quantitative data are lacking to guide the determination of what constitutes normal vibratory amplitude.

METHODS/STUDY DESIGN

Eleven participants were assessed during sustained vowel production using rigid and flexible endoscopy with stroboscopy. Still images were extracted from digital recordings of a sustained /i/ produced at a comfortable pitch and loudness, with F0 controlled so that levels were within ±15% of each participant's comfortable mean level as determined from connected speech. Glottal width (GW), true vocal fold (TVF) length, and TVF width were measured from still frames representing the maximum open phase of the vibratory cycle. To control for anatomic and magnification differences across participants, GW was normalized to TVF length. GW as a ratio of TVF width was also computed for comparison with prior studies.

RESULTS

Mean values and standard deviations were computed for the normalized measures. Paired t tests showed no significant differences between rigid and flexible endoscopy methods. Interrater and intrarater reliability values for raw measurements were found to be high (0.89-0.99).

CONCLUSIONS

These preliminary quantitative data may be helpful in determining normality or abnormality of vocal fold vibration. Results indicate that quantified amplitude of vibration is similar between endoscopic methods, a clinically relevant finding for individuals performing and interpreting stroboscopic assessments.

Aging voice: presbyphonia

Presbyphonia is a physiological process of aging voice that includes morphological changes in the coverage mucosa, muscle, and cartilage. We revised the morphological, endoscopic, and vocal acoustic changes that occur in presbyphonia and discussed some treatments proposed to minimize glottal incompetence and improve vocal performance of the elderly.

Recovery of vibratory function after vocal fold microflap in a rabbit model

OBJECTIVES/HYPOTHESIS

The purpose of this study was to evaluate the return of vibratory function and restoration of vibration amplitude and symmetry after vocal fold microflap surgery.

STUDY DESIGN

Prospective in vivo animal model.

METHODS

Microflap surgery was performed on 30 New Zealand white breeder rabbits. The left vocal fold received a 3-mm epithelial incision and mucosal elevation, while the contralateral vocal fold was left intact to serve as an internal control. Quantitative analysis of amplitude ratio and lateral phase difference were measured using high-speed laryngeal imaging at a frame rate of 10,000 frames per second from animals undergoing evoked phonation on postoperative days 0, 1, 3, 5, and 7.

RESULTS

Quantitative measures revealed a significantly reduced amplitude ratio and lateral phase difference on day 0 after microflap. These impairments of vibratory function on day 0 were associated with separation of the vocal fold's body-cover layer. Amplitude ratio increased significantly by day 3 after microflap, with further increases in vibration amplitude on days 5 and 7. While the amplitude ratio improved significantly on day 3, lateral phase difference decreased significantly on day 3, and returned to normal on days 5 and 7.

CONCLUSIONS

High-speed laryngeal imaging was used to investigate the natural time course of postmicroflap recovery of vibratory function. Results revealed the restoration of vibration amplitude and lateral phase difference by days 3 to 7 after microflap. The time period of improved vibratory function observed in this study coincides with the end of the well-documented inflammatory phase of vocal fold wound repair.

LEVEL OF EVIDENCE

N/A.

The impact of phonation mode and vocal technique on vocal fold closure in young females with normal voice quality

OBJECTIVE

Because voice quality depends substantially on vocal fold closure (VFC), voice therapists try to modify VFC by specific voice techniques or adjustments in phonation mode. This study demonstrates the impact of six different phonation modes on VFC in healthy subjects.

METHODS

For this study, 21 female subjects with normal voice quality were selected. The impact of different phonation modes and voice techniques was examined by fiberoptic laryngovideoendoscopy during different modes of phonation: habitual phonation, high pitch, low pitch, resonance on /m/, Coblenzer's "abspannen," and chant talk. The video recordings were judged by three experienced professionals (two Speech and Language Pathologist and one laryngologist) by means of a visual analog scale.

RESULTS

Statistical analysis showed that only resonance on /m/ significantly improved VFC compared with habitual phonation. All other phonation modes and techniques, except low-pitched phonation, led to a significant worse closure in comparison with the closure at normal pitch. The glottic closure observed by low-pitched phonation was not significantly different than the closure at habitual pitch. Interrater agreement was moderate to very good, depending on the mode of phonation.

CONCLUSIONS

The results of this study allow a better understanding of the impact of phonation mode and vocal therapy techniques on VFC in healthy subjects and give an indication about the impact of these methods to influence VFC.

High-speed digital imaging of the larynx: recent advances

PURPOSE OF REVIEW

This review presents recent advances in high-speed digital imaging (HSDI) of the larynx including data acquisition, data analysis, and clinical applicability.

RECENT FINDINGS

Software designed to summarize the large amounts of data captured with HSDI makes it possible to quantitatively analyze recordings from patients, improving the accuracy of the methodology. The new software has been used in studies of normal individuals, increasing our knowledge of normal vocal fold vibratory behavior. HSDI has also been used in patient populations and shows promise in distinguishing various laryngeal conditions that are difficult to distinguish with other imaging modalities. Studies of postoperative patients with HSDI demonstrate the return of some vibratory characteristics but not others, potentially leading the way to improvements in surgical technique.

SUMMARY

Recent advances in HSDI technology have increased the clinical usefulness of the imaging technology and recent studies demonstrate the clinical applicability of HSDI. However, challenges to widespread clinical use of HSDI remain.

Kymographic characterization of vibration in human vocal folds with nodules and polyps

OBJECTIVES/HYPOTHESIS

Digital kymography (DKG) can provide objective quantitative data about vocal fold vibration, which may help distinguish normal from pathological vocal folds as well as nodules from polyps.

STUDY DESIGN

Case-control study.

METHODS

There were 87 subjects who were separated into three groups: control, nodules, and unilateral polyps, and examined using a high-speed camera attached to an endoscope. Videos were analyzed using a custom MATLAB program, and three DKG line-scan positions (25%, 50%, and 75% of vocal fold length) were used in statistical analyses to compare vocal fold vibrational frequency, amplitude symmetry index (ASI), amplitude order, and vertical and lateral phase difference (VPD and LPD, respectively).

RESULTS

Significant differences among groups were found in all vibrational parameters except frequency. Polyps and nodules groups exhibited greater ASI values (less amplitude symmetry) than the control group. Although the control group consistently showed its largest amplitudes at the midline, the polyps group showed larger amplitudes toward the posterior end of the vocal folds. A significant anterior-posterior pattern in amplitude was not found in the nodules group. LPD values were usually largest (most symmetrical) in the control group, followed by nodules and polyps. LPD at the 25% position allowed for differentiation between polyp and nodule groups. The largest VPD (more pronounced mucosal wave) values were usually found in the control group.

CONCLUSIONS

Vibratory characteristics of normal and pathological vocal folds were quantitatively examined and compared using multiline DKG. These findings may allow for better characterization of pathologies and eventually assist in improving the clinical utility of DKG.

Computation of physiological human vocal fold parameters by mathematical optimization of a biomechanical model

With the use of an endoscopic, high-speed camera, vocal fold dynamics may be observed clinically during phonation. However, observation and subjective judgment alone may be insufficient for clinical diagnosis and documentation of improved vocal function, especially when the laryngeal disease lacks any clear morphological presentation. In this study, biomechanical parameters of the vocal folds are computed by adjusting the corresponding parameters of a three-dimensional model until the dynamics of both systems are similar. First, a mathematical optimization method is presented. Next, model parameters (such as pressure, tension and masses) are adjusted to reproduce vocal fold dynamics, and the deduced parameters are physiologically interpreted. Various combinations of global and local optimization techniques are attempted. Evaluation of the optimization procedure is performed using 50 synthetically generated data sets. The results show sufficient reliability, including 0.07 normalized error, 96% correlation, and 91% accuracy. The technique is also demonstrated on data from human hemilarynx experiments, in which a low normalized error (0.16) and high correlation (84%) values were achieved. In the future, this technique may be applied to clinical high-speed images, yielding objective measures with which to document improved vocal function of patients with voice disorders.

Quantitative study of vibrational symmetry of injured vocal folds via digital kymography in excised canine larynges

PURPOSE

Digital kymography and vocal fold curve fitting are blended with detailed symmetry analysis of kymograms to provide a comprehensive characterization of the vibratory properties of injured vocal folds.

METHOD

Vocal fold vibration of 12 excised canine larynges was recorded under uninjured, unilaterally injured, and bilaterally injured conditions. Kymograms were created at 25%, 50%, and 75% of the vocal fold length, and vibratory parameters were compared quantitatively among conditions and were studied with respect to right-left and anterior-posterior symmetries.

RESULTS

Anterior-posterior amplitude asymmetry was found in the bilateral condition. The unilateral condition showed significant right-left amplitude asymmetry, and it showed the lowest right-left phase symmetry among the conditions. In condition comparisons, vertical phase difference did not show significant differences among conditions, whereas amplitudes were significantly different among conditions at all line scan positions and most vocal fold lips. Significant differences in frequency were found among the conditions at all 4 vocal fold lips, with the bilateral condition exhibiting the greatest frequency.

CONCLUSION

Digital kymography and curve fitting provide detailed information about the vibratory behavior of injured vocal folds. Awareness of vibratory properties associated with vocal fold injury may aid in diagnosis, and the quantitative abilities of digital kymography may allow for objective treatment selection.

Frame by frame analysis of glottic insufficiency using laryngovideostroboscopy

OBJECTIVES/HYPOTHESIS

Glottic insufficiency (GI) can be either grossly obvious or subtle in its presentation. Subtle GI is demonstrated by various Laryngovideostroboscopic (LVS) clues, including complete but "short" phase closure of the true vocal folds (VFs) during the glottic cycle. We used the frame by frame analysis (FBFA) technique to evaluate its effectiveness in objectively contributing to the diagnosis of subtle GI in patients with atrophic and/or paretic VFs. This article intends to formally present the methods and intentions of the FBFA technique and report our findings using FBFA on subjects with clinically diagnosed GI and normal volunteers.

STUDY DESIGN

Retrospective review and demonstration of technique.

METHODS

Forty-four subjects with a prior clinical diagnosis of true VF atrophy (25/44) and/or paresis (19/44) and five normal volunteers were identified. Using the FBFA technique, each subject's average percentage of closed frames per glottic cycle was recorded.

RESULTS

Subjects with atrophy spent 32.4% of the frames of the glottic cycle in the closed phase, subjects with paresis spent 35.7% of the frames closed, and normal subjects spent 50.2% of the frames closed.

CONCLUSIONS

FBFA appears to be a simple objective method for the novice or experienced LVS interpreter, by which one can suspect subtle GI. Because of the inherent physical properties by which LVS gives an "illusionary" representation of the glottic cycle, the FBFA technique remains a theoretical tool. Future studies using high-speed digital imaging are needed to validate this useful technique.

Biomechanical modeling of the three-dimensional aspects of human vocal fold dynamics

Human voice originates from the three-dimensional (3D) oscillations of the vocal folds. In previous studies, biomechanical properties of vocal fold tissues have been predicted by optimizing the parameters of simple two-mass-models to fit its dynamics to the high-speed imaging data from the clinic. However, only lateral and longitudinal displacements of the vocal folds were considered. To extend previous studies, a 3D mass-spring, cover-model is developed, which predicts the 3D vibrations of the entire medial surface of the vocal fold. The model consists of five mass planes arranged in vertical direction. Each plane contains five longitudinal, mass-spring, coupled oscillators. Feasibility of the model is assessed using a large body of dynamical data previously obtained from excised human larynx experiments, in vivo canine larynx experiments, physical models, and numerical models. Typical model output was found to be similar to existing findings. The resulting model enables visualization of the 3D dynamics of the human vocal folds during phonation for both symmetric and asymmetric vibrations.

Differentiated vocal tract control and the reliability of interpretations of nasendoscopic assessment

Training specific vocal techniques can be effective in treating nonorganic dysphonias. Evaluation of vocal function in these studies has included auditory-perceptual assessment, aerodynamic measurement, acoustic analysis, self-report, and visual inspection of the larynx. Reliability of judgments made using visual rating tools for nasendoscopic and videostroboscopic visualization of the larynx when diagnosing vocal function and disorder has been the focus of previous research. However, detailed analysis of factors that affect reliability and consistency of perceptual ratings of laryngoscopic footage has not been investigated in voice therapy outcome studies. This study evaluated clinicians' judgments of the effectiveness of training differentiated vocal tract control of false vocal fold activity (FVFA), true vocal fold mass (TVFM) and larynx height (LH). A within-subject, experimental design was used to assess participants' mastery in manipulating FVFA, TVFM, and LH assessed via laryngoscopic visualization of the larynx. Three experienced speech pathologists rated the nasendoscopy footage with accompanying acoustic recordings of 12 speakers. Intrajudge consistency, interjudge reliability, and interjudge agreement of perceptual ratings were investigated. Twelve vocally trained unimpaired speakers used differentiated biomechanical manipulation of various laryngeal muscles to produce eight specific vocal qualities each. These manipulated vocal qualities were rated by three experienced voice clinicians who demonstrated higher levels of intrajudge consistency and interjudge agreement when identifying rather than quantifying the degree of a voice quality based on their visual and auditory perceptions of the different vocal features. The findings suggest that unimpaired speakers can be trained successfully to manipulate and change individual biomechanical aspects of their vocal functions as demonstrated by the visual- and auditory-perceptual judgments of expert voice clinicians. These judgments are vulnerable to issues of reliability and suggests that judges used auditory-perceptual judgments when interpreting laryngoscopic footage, particularly when the view of laryngeal features is compromised.

Advances in laryngeal imaging

Imaging and image analysis became an important issue in laryngeal diagnostics. Various techniques, such as videostroboscopy, videokymography, digital kymography, or ultrasonography are available and are used in research and clinical practice. This paper reviews recent advances in imaging for laryngeal diagnostics.

New laryngoscope for quantitative high-speed imaging of human vocal folds vibration in the horizontal and vertical direction

We report the design of a novel laser line-triangulation laryngoscope for the quantitative visualization of the three-dimensional movements of human vocal folds during phonation. This is the first successful in vivo recording of the three-dimensional movements of human vocal folds in absolute values. Triangulation images of the vocal folds are recorded at the rate of 4000 fps with a resolution of 256x256 pixels. A special image-processing algorithm is developed to precisely follow the subpixel movements of the laser line image. Vibration profiles in both horizontal and vertical directions are calibrated and measured in absolute SI units with a resolution of +/-50 microm. We also present a movie showing the vocal folds dynamics in vertical cross section.

Voice loudness and gender effects on jitter and shimmer in healthy adults

PURPOSE

The aim of this study was to investigate voice loudness and gender effects on jitter and shimmer in healthy young adults because previous descriptions have been inconsistent.

METHOD

Fifty-seven healthy adults (28 women, 29 men) aged 20-40 years were included in this cross-sectional single-cohort study. Three phonations of /a/ at soft, medium, and loud individual loudness were recorded and analyzed using PRAAT software (P. Boersma & D. Weeninkk, 2006). Voice loudness and gender effects on measured sound pressure level, fundamental frequency, jitter, and shimmer were assessed through the use of descriptive and inferential (analysis of variance) statistics.

RESULTS

Jitter and shimmer significantly increased with decreasing voice loudness, especially in phonations below 75 dB and 80 dB. In soft and medium phonation, men were generally louder and showed significantly less shimmer. However, men had higher jitter measures when phonating softly. Gender differences in jitter and shimmer at medium loudness may be mainly linked to different habitual voice loudness levels.

CONCLUSION

This pragmatic study shows significant voice loudness and gender effects on perturbation. In clinical assessment, requesting phonations above 80 dB at comparable loudness between genders would enhance measurement reliability. However, voice loudness and gender effects in other age groups, in disordered voices, or when a minimal loudness is requested should be further investigated.

Depth-kymography: high-speed calibrated 3D imaging of human vocal fold vibration dynamics

We designed and developed a laser line-triangulation endoscope compatible with any standard high-speed camera for a complete three-dimensional profiling of human vocal fold vibration dynamics. With this novel device we are able to measure absolute values of vertical and horizontal vibration amplitudes, length and width of vocal folds as well as the opening and closing velocities from a single in vivo measurement. We have studied, for the first time, the generation and propagation of mucosal waves by locating the position of its maximum vertical position and the propagation velocity. Precise knowledge about the absolute dimensions of human vocal folds and their vibration parameters has significant importance in clinical diagnosis and treatment as well as in fundamental research in voice. The new device can be used to investigate different kinds of pathological conditions including periodic or aperiodic vibrations. Consequently, the new device has significant importance in investigating vocal fold paralysis and in phonosurgical applications.

Laryngeal and respiratory behavior during pitch change in professional singers

The aim of this study was to examine the physiology of pitch change in terms of laryngeal and respiratory mechanisms in professional singers. Nine female professional singers were recruited to participate in the study. Videoendoscopic recordings of the participants producing one-octave ascending and descending scales were used as a basis to apply a ratio measurement of vocal fold length for each note produced on the scale. Simultaneous respiratory data using Respitrace were also collected. Questionnaires (Voice Handicap Index and Vocal Questionnaire) were used to obtain information about psychosocial aspects related to voice use. Two vocal fold lengthening patterns (static and dynamic) were observed with pitch change. Participants exhibiting a static pattern of vocal fold lengthening had fewer years of vocal training, exhibited a more variable use of vital capacity, and also began the singing task at a higher position in their vital capacity. The reverse was true for participants exhibiting a dynamic vocal fold pattern. These preliminary data indicate that the pattern of vocal fold lengthening exhibited by singers may be related to the number of years of training possessed. Furthermore, the data indicate that stability in one subsystem may result in variability in another, as shown by the interaction between the vocal fold and respiratory patterns.

Outcome of Resonant Voice Therapy for Female Teachers With Voice Disorders: Perceptual, Physiological, Acoustic, Aerodynamic, and Functional Measurements

Teachers have a high percentage of voice problems. For voice disordered teachers, resonant voice therapy is hypothesized to reduce voice problems. No research has been done on the physiological, acoustic, and aerodynamic effects of resonant voice therapy for school teachers. The purpose of this study is to investigate resonant voice therapy outcome from perceptual, physiological, acoustic, aerodynamic, and functional aspects for female teachers with voice disorders. A prospective study was designed for this research. The research subjects were 24 female teachers in Taipei. All subjects received resonant voice therapy in groups of 4 subjects, 90 minutes per session, and 1 session per week for 8 weeks. The outcome of resonant voice therapy was assessed from auditory perceptual judgment, videostroboscopic examination, acoustic measurements, aerodynamic measurements, and functional measurements before and after therapy. After therapy the severity of roughness, strain, monotone, resonance, hard attack, and glottal fry in auditory perceptual judgments, the severity of vocal fold pathology, mucosal wave, amplitude, and vocal fold closure in videostroboscopic examinations, phonation threshold pressure, and the score of physical scale in the Voice Handicap Index were significantly reduced. The speaking Fo, maximum range of speaking Fo, and maximum range of speaking intensity were significantly increased after therapy. No significant change was found in perturbation and breathiness measurements after therapy. Resonant voice therapy is effective for school teachers and is suggested as one of the therapy approaches in clinics for this population.

Influence of Age and Gender on the Dysphonia Severity Index

Attempts have been made to find objective parameters for assessing voice quality for many years. Objective measurements such as the dysphonia severity index (DSI), using four parameters (highest frequency, lowest intensity, maximum phonation time and jitter), appear to correlate well with perceptual evaluation. The aim of this study was to investigate the influence, if any, of age and gender on the DSI. The DSI of 118 non-smoking adults (69 females, 49 males, age range 20-79 years) without voice complaints was measured. Age has a significant effect on the DSI and on its parameters highest frequency and lowest intensity (only in females). Gender has no effect on the DSI, although it has a significant effect on the parameters highest frequency and maximum phonation time. To be able to distinguish between the effects of (normal) ageing and a voice disorder, normative data of a wide age range are essential. As a result of this study normative DSI values for gender and age have been made available.

The Pitch Rise Paradigm: A New Task for Real-Time Endoscopy of Non-Stationary Phonation

As standard stroboscopy is restricted to the recording of periodic vocal fold vibrations, observations of non-stationary laryngeal mechanisms demand real-time recording systems, the most advanced being the high-speed video technique. It allows the registration of laryngeal parameters during a variation of the fundamental frequency. The aim of this study was to compare amplitude and frequency parameters of vocal fold vibration during stationary and non-stationary phonation, i.e. a monotonous pitch rise. Twenty-nine young female adults with no incidence of voice disorders were examined while performing two different phonation tasks: sustained phonation with a constant frequency and a monotonous pitch rise. Endoscopic recordings and the acoustic signals were acquired simultaneously. Both acoustic and laryngeal parameters were derived for short time intervals of 17.8 ms for the constant pitch and pitch rise conditions. Instantaneous frequency, sound pressure level, vibratory amplitudes of the vocal folds and the type of glottal closure were compared. At the beginning of the pitch rise, the acoustic and laryngeal parameters were similar to the parameters that occurred within the sustained phonation conditions. In contrast, the laryngeal parameters at the middle and at the end of the pitch rise differed substantially from those during sustained phonation. For the first time, quantitative measures of the growing glottal chink and the vibration amplitude decrease during pitch increase could be taken. In general, the image evaluation of the pitch rise paradigm can be subdivided into the starting, the raising and the final phase. As each phase can be considered as quasi-stationary, existing software modules are capable of analysing the process by treating each phase separately. Hence, the pitch rise condition may be suitable for clinical examination to detect information of voice disturbances that cannot be visualized during sustained phonation.

Accuracy of measurements on digital videostroboscopic images of the vocal folds

OBJECTIVES

The reliability of objective measurements on digital laryngeal images was investigated.

METHODS

The magnitude of the error of measurement of surface areas by visually tracing the outline was determined for three different areas: the area of the lesion and, during vibration, the glottal area on maximal opening of the vocal folds and the glottal area on maximal closing of the vocal folds.

RESULTS

The errors in these areas were 10% to 30%. The results suggest that the error is mainly due to the uncertainty of the real outline of areas with a vague boundary. Correction for differences in magnification between two images (posttherapy and pretherapy) is of importance in about 25% to 65% of cases, depending on the area measured.

CONCLUSIONS

Only when the magnification ratio is small (less than about +/- 10% from 1.0) may a correction not be necessary.

Glottic Characteristics and Voice Complaint in the Elderly

This study evaluated the relationship between voice complaint and deviant vocal fold status with special regard to presbylarynx, in patients aged more than 60 years, with pharyngeal-laryngeal complaint. The material consisted of clinical histories and images obtained by laryngoscopies from protocols from the Larynx Institute-INLAR, Sao Paulo, Brazil, of 210 patients, 88 men and 122 women, aged more than 60 years, who had sought otorhinolaryngologic treatment. Indicative glottic characteristics of the presbylarynx, such as vocal fold bowing, prominence of vocal processes, and spindle-shaped glottic chink, were analyzed. The increase in mass, leukoplakia, and other vocal fold alterations, distinct from these two, grouped as miscellaneous, as well as the presence or absence of voice complaint were also analyzed. Vocal fold bowing, prominence of vocal processes, and spindle-shaped glottic chink showed a strong correlation among each other. The presence of presbylarynx was accompanied by less voice complaint than the presence of vocal fold mucosa alterations, which in turn are more common where an absence of presbylarynx exists.

Influence of glottal closure configuration on vocal efficacy in young normal-speaking women

Posterior closure insufficiency of the glottis is often mentioned in connection with permanent voice disorders. Recently published studies have revealed that an incomplete closure of the glottis can be found also in normal-speaking voices, especially in women. However, the effect of glottal closure configuration on vocal efficacy is not sufficiently clarified. The purpose of this study was to determine the effect of glottal closure configuration on singing and speaking voice characteristics. Overall, 520 young female normal-speaking subjects were examined by videostroboscopy for different phonation conditions in the combination of soft, loud, low, and/or high phonation and by voice range profile measurements. According to the videostroboscopic analysis, the subjects were subdivided into four groups: complete closure of the vocal folds already in soft phonation (group 1), closure of the vocal fold with increasing intensity (group 2), persistent closure insufficiencies despite increasing intensity (group 3), and hourglass-shaped closure in subjects with vocal nodules (group 4). Subjects in which the glottal closure could not be evaluated sufficiently were subclassified into group 5 (missing values). Selected criteria of the singing and speaking voice were evaluated and statistically processed according to the mentioned subclassification. Group 1 reached significantly the highest sound pressure levels (SPLmax) for the singing voice as well as for the shouting voice. Group 3 showed a limited capacity to increase the intensity of the singing and speaking voice. The results gathered in this study objectify the relationship of insufficient glottal closure and reduced vocal capabilities. As long as no conclusive data on long-term consequences of insufficient glottal closure are available, a prophylactic improvement of the laryngeal situation especially in female professional voice users by voice therapy should be recommended.

Anterior-Posterior and medial compression of the supraglottis: signs of nonorganic dysphoniaor normal postures?

Two vocal tract postures commonly identified as hallmarks of nonorganic dysphonia are anterior-posterior and medial compression of the supraglottis. However, insufficient data exist to support their diagnostic utility. The purpose of this study was to compare these two postures in patients with nonorganic dysphonia and normal controls using interval data derived from quantitative measures of videostroboscopic images obtained with an oral endoscope. Retrospectively, 40 patients with nonorganic dysphonia and 40 normal controls were selected. Relative anterior-posterior compression (LO(AP)) was calculated as the laryngeal outlet (LO) (the view of the true vocal folds during phonation) normalized to the anterior-posterior dimension in pixels. Relative ventricular fold medial compression (LO(w)) was calculated as the laryngeal outlet normalized to the medial dimension in pixels. Results were as follows: (1) LO(AP) was significantly greater for the dysphonic group, (2) the range of LO(AP) values between the two groups overlapped considerably, (3) no significant difference was found between groups for LO(w), (4) the correlation between LO(AP) and LO(w) within each subject yielded r values of 0.71 and 0.67 for the nonorganic dysphonia and normal control groups, respectively. It is concluded that medial compression of the ventricular folds can be a normal laryngeal posture, and that although anterior-posterior compression is present in greater degree in dysphonics, it is sufficiently common in normals to question its utility as a diagnostic sign of phonatory dysfunction.

Lateral phase mucosal wave asymmetries in the clinical voice laboratory

Anecdotally, in some persons it has been observed by the Senior Author (K.K.) that asymmetries of the mucosal wave exist when examined videostroboscopically. In the vast majority of these people, no pathology is ever discovered. Mucosal wave asymmetries could cause concern for the otolaryngologist, who may consider them to be a forewarning of subclinical pathology and subject the patient to unnecessary, expensive, and anxiety-provoking investigations or interventions. The purpose of this study was to establish the prevalence of mucosal wave asymmetries in an asymptomatic population lacking laryngeal pathology. Acoustic spectral analysis is also utilized to determine if the presence of subharmonics might be associated. A hospital-based, cross-sectional study design was used. The subjects had no known vocal or medical pathologies, and were nonsmoking. The study group was composed of 30 males aged 35-50 years and 30 women between 22-55 years. Each of the males underwent acoustic spectral analysis; and all subjects completed a medical questionnaire, subjective talkativeness rating, and videostroboscopic laryngeal examination. 10.5% of the subjects (exact 95% CI = 4.0-21.5%) exhibited mucosal wave variations at stroboscopy, characterized as periodic lateral phase asymmetries found consistently in both the modal and upper registers. There was no association with the chosen acoustic spectral parameters, talkativeness scales, or questionnaire-based variables. Mucosal wave asymmetries may be a variance of normal, and are likely to be far more common in the general population than previously believed. The prevalence detected here is expected to be important in the clinical laryngology practice, where these asymmetries may be frequently encountered and influencing management decisions. There has been little normative data published for variations of the mucosal wave specifically for epidemiological purposes. Clinically, in the absence of such data, otolaryngologists may over interpret videostroboscopic findings, leading to unnecessary investigations or interventions.

Effects of voice therapy as objectively evaluated by digitized laryngeal stroboscopic imaging

Objective measurements derived from digitized laryngeal stroboscopic images were used to demonstrate changes in vocal fold vibration and in the size of benign lesions after 3 months of voice therapy. Forty chronically dysphonic patients were studied. By means of a rigid stroboscope, pretreatment and posttreatment recordings were made of the vocal folds at rest and under stroboscopic light during phonation. From each recording, images of the positions at rest and during vibration at maximal opening and at maximal closure were digitized. The surface areas of any lesions and of the glottal gap were independently measured in the digitized images by 2 experienced laryngologists. Referential distances were determined in order to compensate for discrepancies in magnification in the various recordings. After 3 months of voice therapy, significant improvement in lesion size and degree of maximal closure during vibration could be demonstrated in about 50% of the patients. The degree of maximal opening did not prove to be a significant parameter.

On the influence of laryngeal pathologies on acoustic and electroglottographic jitter measures

This study compared acoustic and electroglottographic (EGG) jitter from [a] vowels of 103 dysphonic speakers. The EGG recordings were chosen according to their intensity, signal-to-noise ratio, and percentage of unvoiced intervals, while acoustic signals were selected based on voicing detection and the reliability of jitter extraction. The agreement between jitter measures was expressed numerically as a normalized difference. In 63.1% (65/103) of the cases the differences fell within +/-22.5%. Positive differences above +22.5% were associated with increased acoustic jitter and occurred in 12.6% (13/103) of the speakers. These were, typically, cases of small nodular lesions without problems in the posterior larynx. On the other hand, substantial rises in EGG jitter leading to differences below -22.5% took place in 24.3% (25/103) of the speakers and were related to hyperfunctional voices, creaky-like voices, small laryngeal asymmetries affecting the arytenoids, or small-to-moderate glottal chinks. A clinically relevant outcome of the study was the possibility of detecting gentle laryngeal asymmetries among cases of large unilateral increase in EGG jitter. These asymmetries can be linked with vocal problems that are often overlooked in endoscopic examinations.

Formants of children, women, and men: the effects of vocal intensity variation

The purpose of this study was to investigate the formant frequencies and amplitudes of a wide age range of children and one group of adults at three sound pressure levels (SPLs). Subjects were ten females and ten males in the following age groups (in years): 4, 6, 8, 10, 12, 14, 16, 18, and adults. A sustained /a/ was produced three times by each subject. Formant frequencies were obtained using linear predictive coding analysis. Formant amplitudes were measured from the highest amplitude harmonic in the area of each formant. In addition to following established trends previously published in other studies, it was hypothesized that the first formant frequency would increase with increasing intensity, that females would have higher formant frequencies than same aged males, and that women and children would have reduced formant amplitudes as compared to men. It was found that first formant frequency increased with intensity and changed as a function of age and sex. Second and third formant frequencies changed with age and sex. Formant amplitudes followed the trends set by the SPL differences and did not change as a function of age and sex. Results are discussed in terms of anatomic differences and SPL.