Acoustic characteristics of phonation in "wet voice" conditions

A Scoping Review on the Intersection Between Voice and Swallowing Measures in Healthy and Disordered Populations

PURPOSE

Voice and swallowing are distinct functions that share anatomical and physiological properties; however, research investigating their intersection is limited. The purpose of this scoping review was to explore the literature surrounding the relationship between voice and swallowing measures in healthy adults and those with non-degenerative disorders. Specifically, we aimed to elucidate whether objective voice measures could be used as correlates of swallowing function.

METHOD

We systematically searched four databases (Embase, PubMed, CINAHL, and Web of Science) for relevant literature using a combination of key words and controlled vocabulary generated from the Yale Mesh Analyzer. The inclusion criteria consisted of peer-reviewed studies in the English language that reported on healthy adults and/or patients with non-degenerative neurological disorders and pulmonary diseases and contained instrumental and/or objective voice and swallowing measures. Two raters completed the abstract screening process followed by independent full-text reviews. Case studies, review studies, gray literature, or abstract-only studies were excluded.

RESULTS

Among 5,485 screened studies, 182 were fully reviewed, with only 11 studies meeting the inclusion criteria. Eight studies found an association between voice and swallowing objective measures, whereas the other three did not. Significant voice measures that were related to swallowing safety and/or physiology included maximum fundamental frequency (F0), F0 range, maximum phonation time, biomechanics of effortful pitch glides, and voice onset time.

CONCLUSIONS

Although there was heterogeneity in the measures used, specific objective voice measures showed promise in clinical practice as a screening tool for dysphagia. Further investigations are needed to validate the clinical utility of these measures across diverse patient populations.

Eliciting and Characterizing Porcine Vocalizations: When Pigs Fly

BACKGROUND/OBJECTIVES

While voice-related therapeutic interventions are often researched preclinically in the porcine model, there are no well-established methods to induce porcine glottic phonation. Described approaches, such as training animals to phonate for positive reinforcement are time-consuming and plagued by inherent variability in the type of phonation produced and contamination of background noise. Thus, a reliable method of assessing glottic phonation in the porcine model is needed.

METHODS

In this study, we have created a novel pulley-based apparatus with harness for "pig-lifting" with surrounding acoustic insulation and high-directional microphone with digital recorder for recording phonation. Praat and Matlab were used to analyze all porcine vocalizations for fundamental frequency (F0), intensity, duration of phonation and cepstral peak prominence (CPP). Glottic phonation was detected using F0 (≥2000 hz), duration (≥3 seconds) and researcher perceptual judgment. Partial-glottic phonations were also analyzed. Reliability between researcher judgment and acoustic measures for glottic phonation detection was high.

RESULTS

Acoustic analysis demonstrated that glottic and partial-glottic phonation was consistently elicited, with no formal training of the minipigs required. Glottic vocalizations increased with multiple lifts. Glottic phonation continued to be elicited after multiple days but became less frequent. Glottic and partial-glottic phonations had similar CPP values over the 6 experimental days.

CONCLUSION

Our cost-effective, reliable method of inducing and recording glottic phonation in the porcine model may provide a cost effective, preclinical tool in voice research.

The oral organ: A new vision of the mouth as a whole for a gerophysiological approach to healthy aging

This article brings a new perspective on oral physiology by presenting the oral organ as an integrated entity within the entire organism and its surrounding environment. Rather than considering the mouth solely as a collection of discrete functions, this novel approach emphasizes its role as a dynamic interphase, supporting interactions between the body and external factors. As a resilient ecosystem, the equilibrium of mouth ecological niches is the result of a large number of interconnected factors including the heterogeneity of different oral structures, diversity of resources, external and internal pressures and biological actors. The manuscript seeks to deepen the understanding of age-related changes within the oral cavity and throughout the organism, aligning with the evolving field of gerophysiology. The strategic position and fundamental function of the mouth make it an invaluable target for early prevention, diagnosis, treatment, and even reversal of aging effects throughout the entire organism. Recognizing the oral cavity capacity for sensory perception, element capture and information processing underscores its vital role in continuous health monitoring. Overall, this integrated understanding of the oral physiology aims at advancing comprehensive approaches to the oral healthcare and promoting broader awareness of its implications on the overall well-being.

Machine learning in the evaluation of voice and swallowing in the head and neck cancer patient

PURPOSE OF REVIEW

The purpose of this review is to present recent advances and limitations in machine learning applied to the evaluation of speech, voice, and swallowing in head and neck cancer.

RECENT FINDINGS

Novel machine learning models incorporating diverse data modalities with improved discriminatory capabilities have been developed for predicting toxicities following head and neck cancer therapy, including dysphagia, dysphonia, xerostomia, and weight loss as well as guiding treatment planning. Machine learning has been applied to the care of posttreatment voice and swallowing dysfunction by offering objective and standardized assessments and aiding innovative technologies for functional restoration. Voice and speech are also being utilized in machine learning algorithms to screen laryngeal cancer.

SUMMARY

Machine learning has the potential to help optimize, assess, predict, and rehabilitate voice and swallowing function in head and neck cancer patients as well as aid in cancer screening. However, existing studies are limited by the lack of sufficient external validation and generalizability, insufficient transparency and reproducibility, and no clear superior predictive modeling strategies. Algorithms and applications will need to be trained on large multiinstitutional data sets, incorporate sociodemographic data to reduce bias, and achieve validation through clinical trials for optimal performance and utility.

Acoustic Screening of the "Wet voice": Proof of Concept in an ex vivo Canine Laryngeal Model

BACKGROUND

Current protocols for bedside swallow evaluation have high rates of false negative results. Though experts are not consistently able to screen for aspiration risk by assessing vocal quality, there is emerging evidence that vocal acoustic parameters are significantly different in patients at risk of aspiration. Herein, we aimed to determine whether the presence of material on the vocal folds in an excised canine laryngeal model may have an impact on acoustic and aerodynamic measures.

METHODS

Two ex vivo canine larynges were tested. Three liquids of different viscosities (1:100 diluted glycerin, pure glycerin, and honey-thick Varibar) were placed on the vocal folds at a constant volume. Acoustic and aerodynamic measures were obtained in both adducted and abducted vocal fold configurations. Intraglottal high-speed imaging was used to approximate the maximum divergence angle of the larynges in the studied conditions and examine its relationship to vocal efficiency (VE) and acoustic measures.

RESULTS

In glottic insufficiency conditions only, we found that several acoustic parameters could predict the presence of material on the vocal folds. Based on the combination of the aerodynamic and acoustic data, we found that decreased spectral energy in the higher harmonics was associated with decreased VE in the presence of material on the vocal folds and/or glottic insufficiency.

CONCLUSION

Decreased spectral energy in the higher harmonics of the voice was found to be a potential biomarker of swallowing dysfunction, as it correlates with decreased vocal efficiency due to material on the vocal folds and/or glottic insufficiency, both of which are known risk factors for aspiration.

LEVEL OF EVIDENCE

NA Laryngoscope, 133:2517-2524, 2023.

Swallow Impairment in Parkinson's Disease: Revelations from High-Resolution Videomanometry

Parkinson's disease (PD) is a degenerative disorder that can cause dysphagia and dysphonia. We studied upper esophageal sphincter (UES) function and vocal tests using high-resolution videomanometry (HRVM) in PD. Ten healthy volunteers and 20 patients with PD performed swallowings (5 ml and 10 ml) and vocal tests using HRVM synchronized to the vocal acoustic recording. Mean age of the Parkinson group was 68.7 ± 9.7 years and mean disease stage of 2.7 ± 1.1 (Hoehn & Yahr scale). In videofluoroscopy swallow study (VFSS) for 5 ml, laryngeal elevation was significantly reduced (p = 0.01) in PD and for 10 ml, anteriorization (p = 0.03), elevation (p = 0.03) and total displacement (p = 0.05) were reduced in PD. In high-resolution manometry (HRM) for both volumes, intrabolus pressure was significantly higher in PD (p = 0.0004 and p = 0.001) and a higher NADIR UES relaxation pressure and NADIR UES relaxation at pharyngeal peak contraction in PD (p = 0.00007 and p = 0.0003, p = 0.01 and p = 0.04), respectively. Vocal tests results showed differences between the groups, especially for larynx anteriorization with high pitch /a/ emission (p = 0.06) in VFSS and for UES length with high pitch /i/ with tongue protrusion (p = 0.07) in HRM. Our results demonstrated a reduced compliance and subtle changes in UES function in early and moderate PD stage. We also demonstrated using HRVM that vocal tests can affect UES function. The use of HRVM proved to be an important tool in the description of events related to phonation and swallowing, which can affect the rehabilitation of patients with PD.

Aspiration Risk Screening With Tongue Pressure Measurement in Acute Stroke: A Diagnostic Accuracy Study Using STARD Guidelines

Introduction

Dysphagia can affect more than 50% of stroke patients in the acute phase. Aspiration pneumonia is a serious complication that can be prevented with dysphagia screening and assessment. Measurement of tongue elevation pressure is suggested to be a useful tool in aspiration risk screening.

Objective

This study aimed to assess the diagnostic accuracy of maximum anterior tongue elevation strength (Pmax) in acute stroke care.

Method

In this prospective study, data were collected in a neurology department (stroke center) where patients formed a consecutive case series. The sample consisted of thirty stroke patients who failed an initial dysphagia screening. Patients underwent anterior tongue elevation strength measurement (index test) during bedside dysphagia assessment by a speech-language pathologist and flexible endoscopic evaluation of swallowing (reference test) by an otorhinolaryngologist on the same day. Outcome variables (index values in kPa, reference values interpreted on the penetration-aspiration scale) were used for estimating measures of diagnostic accuracy in aspiration risk screening.

Results

Ten patients aspirated on instrumental evaluation. At the cut-off point of ≤ 34 kPa the analysis showed 90% sensitivity, 35% specificity, 41% positive predictive value, and 88% negative predictive value. The area under the curve (AUC) for Pmax was AUC = 0.700 (95% CI [0.500-0.900]).

Conclusion

Although individuals with low anterior tongue elevation strength tend to have a higher risk of aspiration, this variable alone is not capable of screening aspiration in acute stroke. In combination with a thorough noninstrumental bedside examination, it might have the potential to reduce the number of false positive cases. Further studies in this area would be worthwhile.

Listening for Dysphagia: Voice Quality Sequelae of Material in the Airway

PURPOSE

Postswallow voice abnormality is often assumed to indicate the presence of material in the laryngeal airway (MIA), but prior research has not shown definitive evidence of a causal relationship. This study investigated if endoscopically confirmed MIA (prandial material or secretions) generates specific voice quality attributes that can be perceptually identified by experienced listeners.

METHOD

Forty-four dysphagic adults underwent endoscopic evaluation of swallowing. Time-linked audiovisual recordings of pre- and postswallow phonation were analyzed to determine the presence, amount, and location of prandial material or secretions in the larynx during phonation. Expert listeners completed auditory-perceptual ratings of phonation samples.

RESULTS

Voice quality ratings did not differ significantly when there was MIA during postswallow phonation. However, judgments of voice quality abnormality for MIA samples were elevated when analyses controlled for effects of baseline dysphonia. Listeners were most likely to perceive voice quality abnormality when larger amounts of secretions were present, as compared to prandial material. Interrater reliability was variable and ranged from low to moderate across perceptual parameters.

CONCLUSIONS

MIA during phonation occurred for many participants, but perception of voice quality abnormality was variable when MIA was present. Baseline dysphonia is common among individuals with dysphagia and may limit perception of voice quality abnormalities generated by MIA. Secretions in the laryngeal airway may have a greater impact on voice quality parameters.

Machine learning based analysis of speech dimensions in functional oropharyngeal dysphagia

BACKGROUND AND OBJECTIVE

The normal swallowing process requires a complex coordination of anatomical structures driven by sensory and cranial nerves. Alterations in such coordination cause swallowing malfunctions, namely dysphagia. The dysphagia screening methods are quite subjective and experience dependent. Bearing in mind that the swallowing process and speech production share some anatomical structures and mechanisms of neurological control, this work aims to evaluate the suitability of automatic speech processing and machine learning techniques for screening of functional dysphagia.

METHODS

Speech recordings were collected from 46 patients with functional oropharyngeal dysphagia produced by neurological causes, and 46 healthy controls. The dimensions of speech including phonation, articulation, and prosody were considered through different speech tasks. Specific features per dimension were extracted and analyzed using statistical tests. Machine learning models were applied per dimension via nested cross-validation. Hyperparameters were selected using the AUC - ROC as optimization criterion.

RESULTS

The Random Forest in the articulation related speech tasks retrieved the highest performance measures (AUC=0.86±0.10, sensitivity=0.91±0.12) for individual analysis of dimensions. In addition, the combination of speech dimensions with a voting ensemble improved the results, which suggests a contribution of information from different feature sets extracted from speech signals in dysphagia conditions.

CONCLUSIONS

The proposed approach based on speech related models is suitable for the automatic discrimination between dysphagic and healthy individuals. These findings seem to have potential use in the screening of functional oropharyngeal dysphagia in a non-invasive and inexpensive way.

Using Voice Change as an Indicator of Dysphagia: A Systematic Review

Voice change post-swallow, observed during a clinical swallow examination, is often used as a clinical indicator of dysphagia risk. However, there has been limited research that evaluated the level of agreement between voice change and swallow dysfunction reported to date. This systematic review aims to investigate existing evidence relating to the relationship between vocal change post-swallow and swallow deficits identified on a Videofluoroscopic Swallow Study (VFSS). The studies were selected by two independent evaluators for inclusion, without restriction on language or date of publication and the methodological quality and the risk of bias were assessed using QUADAS-2. Following the PRISMA recommendation, 271 articles were analyzed, of which 17 were included in the study. Of these, the methodology described in five studies employed voice analyses using only acoustic methods, seven others conducted only auditory-perceptual analyses, and five other studies used both. Across the studies there was no homogeneity in the voice quality parameters assessed, analytic methods used, and results obtained. Forty seven per cent of the studies presented a high risk of bias in the analysis of vocal quality due to lack of clarity and blinding of VFSS. There was no homogeneity in the choice of consistencies evaluated during swallowing, as well as standardization of the outcome investigated in VFSS without a vocal parameter attributable to accurate detection in each outcome. It is not possible to obtain a consensus regarding the recommendation of the use of vocal evaluation as an accurate method for identifying swallowing alterations due to heterogeneity of the vocal evaluation methods, the outcomes evaluated in the VFSS examination, heterogeneity in food and liquid consistencies, and the methodological quality of the studies.

Postswallow voice modification: compatibility with videofluoroscopy findings

PURPOSE

Verify whether voice modification after swallowing is associated with videofluoroscopic examination data.

METHODS

27 patients with oropharyngeal dysphagia underwent recording of sustained phonation of vowel /a/ before and after swallowing during videofluoroscopy. The GRBAS scale and the wet voice parameter were used to evaluate the data. Videofluoroscopy results showed stasis of food in the valleculae and piriform recesses, laryngeal penetration, tracheal aspiration, and degree of dysphagia.

RESULTS

Decreased dysphonia grade and asthenia and increased strain were observed after swallowing, with no difference for the wet voice parameter. Sensitivity and specificity of ± 50% were observed for food stasis in the valleculae and piriform recesses. Sensitivity values of 80 and 66-75% were observed for detection of laryngeal penetration and tracheal aspiration and modification of vocal strain, respectively. Negative predictive values of 77-91% were found for the three assessment parameters with no correlation with the degree of oropharyngeal dysphagia.

CONCLUSION

Modification of the GRBAS scale parameters after swallowing showed good compatibility with videofluoroscopy findings.

Voice and endocrinology

Voice is one of the advanced features of natural evolution that differentiates human beings from other primates. The human voice is capable of conveying the thoughts into spoken words along with a subtle emotion to the tone. This extraordinary character of the voice in expressing multiple emotions is the gift of God to the human beings and helps in effective interpersonal communication. Voice generation involves close interaction between cerebral signals and the peripheral apparatus consisting of the larynx, vocal cords, and trachea. The human voice is susceptible to the hormonal changes throughout life right from the puberty until senescence. Thyroid, gonadal and growth hormones have tremendous impact on the structure and function of the vocal apparatus. The alteration of voice is observed even in physiological states such as puberty and menstruation. Astute clinical observers make out the changes in the voice and refer the patients for endocrine evaluation. In this review, we shall discuss the hormonal influence on the voice apparatus in normal and endocrine disorders.

Permeability of canine vocal fold lamina propria

OBJECTIVES/HYPOTHESIS

Determine the permeability of excised canine vocal fold lamina propria.

STUDY DESIGN

Basic science.

METHODS

Vocal folds were excised from canine larynges and mounted within a device to measure the flow of 0.9% saline through the tissue over time. The resultant fluid volume displaced over time was then used in a variation of Darcy's law to calculate the permeability of the tissue. Permeability was found through each anatomical plane of the vocal fold, with five samples per plane. Permeability was also found for lamina propria stretched to 10%, 20%, and 30% of its initial length to determine the effects of tensile strain on permeability, with five samples per level of strain.

RESULTS

Permeability was found to be 1.40 × 10(-13) m(3) s/kg through the sagittal plane, 1.00 × 10(-13) m(3) s/kg through the coronal plane, and 4.02 × 10(-13) m(3) s/kg through the axial plane. It was significantly greater through the axial plane than both the sagittal (P = .025) and coronal (P = .009) planes. Permeability under strain through the sagittal plane was found to be 1.94 × 10(-13) m(3) s/kg under 10% strain, 3.35 × 10(-13) m(3) s/kg under 20% strain, and 4.80 × 10(-13) m(3) s/kg under 30% strain. The permeability significantly increased after 20% strain (P < .05).

CONCLUSIONS

Permeability in canine vocal fold lamina propria was found to be increased along the anterior-posterior axis, following the length of the vocal folds. This may influence fluid distribution within the lamina propria during and after vibration. Similarly, permeability increased after 20% strain was imposed on the lamina propria, and may influence vocal fold dynamics during certain phonation tasks.

LEVEL OF EVIDENCE

NA Laryngoscope, 125:941-945, 2015.

Vocal Variability Post Swallowing in Individuals with and without Oropharyngeal Dysphagia

Introduction Voice modification after swallowing may indicate changes in the transit of the bolus.

Objective The aim of this study is to verify the use of perceptual voice analysis to detect oropharyngeal dysphagia.

Study Design Case series.

Methods Twenty-seven patients with dysphagia as diagnosed by videofluoroscopy and 25 without were evaluated. The sustained vowel /a/ was recorded before this exam and after swallowing different consistencies (pasty, liquid and solid). For the voice evaluation, the GRBAS scale (grade, roughness, breathiness, asthenia and strain) and the parameter “wet voice” were used. Three judges blinded to study group and time of emission performed voice analysis.

Results Individuals with dysphagia showed significant decrease in grade of voice and asthenia and increase in strain after swallowing pasty substances, differing from individuals without dysphagia who showed no modification of the parameters after swallowing. The wet voice parameter showed no difference after swallowing in both study groups.

Conclusion The decrease in grade and asthenia and increased strain are indicative of a swallowing disorder, indicating increased vocal strain to clean the vocal tract of food. The modification of vocal production after swallowing proved to be a trusted resource for detection of swallowing disorders.

Differences in shimmer across formant regions

OBJECTIVES

Objective acoustic measures used to analyze phonatory dysfunction include shimmer and jitter. These measures are limited in that they do not take into account auditory processing. However, previous studies have indicated that shimmer may be processed differently along the tonotopic axis of the ear and, in particular, may be perceptually and physiologically significant around the third and fourth formants.

METHODS

This study investigated the relationship between shimmer around the first four formants (F1-F4) and in the broadband unfiltered speech waveform for 18 normal speakers from the voice disorders database of KayPENTAX. The voice samples were filtered around each formant with a bandwidth of 400Hz and then shimmer was assessed using five built-in different measures from Praat software.

RESULTS

Comparisons of means tests revealed that shimmer increases significantly with formant frequency from F1 to F4, for all shimmer measures. Furthermore, for all shimmer measures, shimmer in the unfiltered speech was significantly and more strongly correlated with shimmer around F1 (r = 0.45-0.61) and F2 (r = 0.69-0.74), significantly but more weakly correlated with F4 (r = 0.42-0.47), and not significantly correlated with F3.

CONCLUSIONS

The findings indicate that there are differences in the shimmer found around the different formants and that shimmer information around F3 and F4 is not well captured in standard shimmer measurements based on the broadband unfiltered waveform.

Experiments on Analysing Voice Production: Excised (Human, Animal) and In Vivo (Animal) Approaches

Experiments on human and on animal excised specimens as well as in vivo animal preparations are so far the most realistic approaches to simulate the in vivo process of human phonation. These experiments do not have the disadvantage of limited space within the neck and enable studies of the actual organ necessary for phonation, i.e., the larynx. The studies additionally allow the analysis of flow, vocal fold dynamics, and resulting acoustics in relation to well-defined laryngeal alterations.

PURPOSE OF REVIEW

This paper provides an overview of the applications and usefulness of excised (human/animal) specimen and in vivo animal experiments in voice research. These experiments have enabled visualization and analysis of dehydration effects, vocal fold scarring, bifurcation and chaotic vibrations, three-dimensional vibrations, aerodynamic effects, and mucosal wave propagation along the medial surface. Quantitative data will be shown to give an overview of measured laryngeal parameter values. As yet, a full understanding of all existing interactions in voice production has not been achieved, and thus, where possible, we try to indicate areas needing further study.

RECENT FINDINGS

A further motivation behind this review is to highlight recent findings and technologies related to the study of vocal fold dynamics and its applications. For example, studies of interactions between vocal tract airflow and generation of acoustics have recently shown that airflow superior to the glottis is governed by not only vocal fold dynamics but also by subglottal and supraglottal structures. In addition, promising new methods to investigate kinematics and dynamics have been reported recently, including dynamic optical coherence tomography, X-ray stroboscopy and three-dimensional reconstruction with laser projection systems. Finally, we touch on the relevance of vocal fold dynamics to clinical laryngology and to clinically-oriented research.