The influence of pitch and loudness changes on the acoustics of vocal tremor

Treatment of Essential Vocal Tremor: A Scoping Review of Evidence-Based Therapeutic Modalities

OBJECTIVES/HYPOTHESIS

Essential vocal tremor (EVT) is an uncommon but challenging condition to manage. Several medical and interventional treatment options have been reported but efficacy remains unclear. We performed a scoping review of high-quality clinical trials to identify effective evidence-based treatments for EVT.

STUDY DESIGN

Scoping review.

METHODS

Relevant studies were identified using the databases MedLine, Cochrane Central Register of Controlled Trials, and Embase. Subjective and objective outcomes for each modality were analyzed and the effect sizes were quantified using Hedges' g measure to allow comparison between studies.

RESULTS

We identified 421 studies eligible for screening with 11 included in the final analysis. Evidence supporting effective EVT treatments was found for bilateral versus unilateral deep brain stimulation (DBS) (Hedges' g 0.65, 95% CI = 0.10-1.20) and octanoic acid (Hedges' g 1.15, 95% CI = 0.40-1.90). Evidence to support the use of methazolamide was not sufficient (Hedges' g 0.51, 95% CI = -0.64 to 1.66). Botulinum toxin (BT) injections were equivalent when comparing unilateral versus bilateral (Hedges' g -0.18, 95% CI = -1.06 to 0.70); BT did not display any advantage over propranolol (Hedges' g -0.47, 95% CI = -1.73 to 0.78) or injection augmentation (Hedges' g 0.068, 95% CI = -0.98 to 1.12).

CONCLUSIONS

Our review finds very little high-quality evidence supporting any treatment for EVT. Octanoic acid reduced fluctuations in EVT but did not affect the perception of the tremor. In refractory cases, bilateral DBS was superior to unilateral DBS in improving subjective voice outcomes. Unilateral and bilateral BT injections were equivalent, and BT injection was not more effective than injection augmentation. Further direct comparison in well-designed prospective studies may help clarify optimal treatment for EVT patients.

Speech, voice, and language outcomes following deep brain stimulation: A systematic review

BACKGROUND

Deep brain stimulation (DBS) reliably ameliorates cardinal motor symptoms in Parkinson's disease (PD) and essential tremor (ET). However, the effects of DBS on speech, voice and language have been inconsistent and have not been examined comprehensively in a single study.

OBJECTIVE

We conducted a systematic analysis of literature by reviewing studies that examined the effects of DBS on speech, voice and language in PD and ET.

METHODS

A total of 675 publications were retrieved from PubMed, Embase, CINHAL, Web of Science, Cochrane Library and Scopus databases. Based on our selection criteria, 90 papers were included in our analysis. The selected publications were categorized into four subcategories: Fluency, Word production, Articulation and phonology and Voice quality.

RESULTS

The results suggested a long-term decline in verbal fluency, with more studies reporting deficits in phonemic fluency than semantic fluency following DBS. Additionally, high frequency stimulation, left-sided and bilateral DBS were associated with worse verbal fluency outcomes. Naming improved in the short-term following DBS-ON compared to DBS-OFF, with no long-term differences between the two conditions. Bilateral and low-frequency DBS demonstrated a relative improvement for phonation and articulation. Nonetheless, long-term DBS exacerbated phonation and articulation deficits. The effect of DBS on voice was highly variable, with both improvements and deterioration in different measures of voice.

CONCLUSION

This was the first study that aimed to combine the outcome of speech, voice, and language following DBS in a single systematic review. The findings revealed a heterogeneous pattern of results for speech, voice, and language across DBS studies, and provided directions for future studies.

The Effects of Remote Signal Transmission and Recording on Acoustical Measures of Simulated Essential Vocal Tremor: Considerations for Remote Treatment Research and Telepractice

PURPOSE

Studies on medical and behavioral interventions for essential vocal tremor (EVT) have shown inconsistent effects on acoustical and perceptual outcome measures across studies and across participants. Remote acoustical and perceptual assessments might facilitate studies with larger samples of participants and repeated measures that could clarify treatment effects and identify optimal treatment candidates. Furthermore, remote acoustical and perceptual assessment might allow clinicians to monitor clients' treatment responses and optimize treatment approaches during telepractice. Thus, the purpose of this study was to evaluate the accuracy of remote signal transmission and recording for acoustical and perceptual assessment of EVT.

METHOD

Simulations of EVT were produced using a computational model and were recorded using local and remote procedures to represent client- and clinician-end recordings respectively. Acoustical analyses measured the extent and rate of fundamental frequency (fo) and intensity modulation to represent vocal tremor severity and the cepstral peak prominence (CPPS) to represent voice quality. The data were analyzed using repeated measures analysis of variance (ANOVA) with recording as the within-subjects factor and sex of the computational model as the between-subjects factor.

RESULTS

There was a significant main effect of recording on the rate of fo modulation and significant interactions of recording and sex for the extent of intensity modulation, rate of intensity modulation, and CPPS. Posthoc pairwise comparisons and analysis of effect size indicated that recording procedures had the largest effect on the extent of intensity modulation for male simulations, the rate of intensity modulation for male and female simulations, and the CPPS for male and female simulations. Despite having disabled all known software and computer audio enhancing options and having stable ethernet connections, there was inconsistent attenuation of signal amplitude in remote recordings that was most problematic for samples with a breathy voice quality but also affected samples with typical and pressed voice qualities.

CONCLUSIONS

Acoustical measures that correlate to perception of vocal tremor and voice quality were altered by remote signal transmission and recording. In particular, signal transmission and recording in Zoom altered time-based estimates of intensity modulation and CPPS with male and female simulations of EVT and magnitude-based estimates of intensity modulation with male simulations of EVT. In contrast, signal transmission and recording in Zoom minimally altered time- and magnitude-based estimates of fo modulation with male and female simulations of EVT. Therefore, acoustical and perceptual assessments of EVT should be performed using audio recordings that are collected locally on the participant- or client-end, particularly when measuring modulation of intensity and CPP or estimating vocal tremor severity and voice quality. Development of procedures for collecting local audio recordings in remote settings may expand data collection for treatment research and enhance telepractice.

Breathy Voice as a Compensatory Strategy for Essential Vocal Tremor: A Single Case Experiment Across Participants

OBJECTIVE

Essential vocal tremor (EVT) manifests as nearly rhythmic modulations of fundamental frequency (fo) and intensity and causes a shaky voice. Although research on behavioral therapy for EVT is limited, previous studies have shown that a breathy voice reduces the perception of simulated EVT and might be an effective compensatory strategy. The current study aimed to measure the acoustical and perceptual effects of a breathy voice strategy in speakers with EVT.

STUDY DESIGN

A single-case experimental design (SCED) was used to investigate acoustical effects, and a pair comparison listening task was used to investigate perceptual effects.

METHODS

Three participants with EVT matched five different levels of breathiness produced by a computational model. Acoustical analyses of the rate and extent of fo and intensity modulation were performed to estimate EVT severity for baseline and treatment trials. Statistical analyses were completed using Tau-U. Twenty novice listeners participated in the perceptual study to determine if treatment trials sounded less "shaky" than baseline trials. Statistical analyses were completed using one sample t tests.

RESULTS

The acoustical effects were variable across different levels of breathiness for all three participants. All participants were able to adjust their levels of breathiness based on auditory models and verbal cues but did not achieve the target levels of breathiness. Listeners did not perceive the breathy trials to be less "shaky" than baseline trials for any level of breathiness.

CONCLUSION

The breathy voice strategy had variable effects on the acoustical measures of EVT, supporting the use of a single-case experimental design to investigate the effectiveness of behavioral treatment for EVT. Listeners perceived breathy trials to be "shakier" than baseline trials, which was inconsistent with our hypothesis and previous studies of EVT. Future research should evaluate the use of a breathy voice in speakers with confirmed laryngeal tremor, optimize cueing for breathiness, and provide more opportunities to practice the breathy strategy.

A Cross-sectional Study of Perceptual and Acoustic Voice Characteristics in Healthy Aging

PURPOSE

The human voice qualitatively changes across the lifespan. Although some of these vocal changes may be pathologic, other changes likely reflect natural physiological aging. Normative data for voice characteristics in healthy aging is limited and disparate studies have used a range of different acoustic features, some of which are implicated in pathologic voice changes. We examined the perceptual and acoustic features that predict healthy aging.

METHOD

Participants (N = 150) aged between 50 and 92 years performed a sustained vowel task. Acoustic features were measured using the Multi-Dimensional Voice Program and the Analysis of Dysphonia in Speech and Voice. We used forward and backward variable elimination techniques based on the Bayesian information criterion and linear regression to assess which of these acoustic features predict age and perceptual features. Hearing thresholds were determined using pure-tone audiometry tests at frequencies 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, and 4000 Hz. We further explored potential relationships between these acoustic features and clinical assessments of voice quality using the Consensus Auditory-Perceptual Evaluation of Voice.

RESULTS

Chronological age was significantly predicted by greater voice turbulence, variability of cepstral fundamental frequency, low relative to high spectral energy, and cepstral intensity. When controlling for hearing loss, age was significantly predicted by amplitude perturbations and cepstral intensity. Clinical assessments of voice indicated perceptual characteristics of speech were predicted by different acoustic features. For example, breathiness was predicted by the soft phonation index, mean cepstral peak prominence, mean low-high spectral ratio, and mean cepstral intensity.

CONCLUSIONS

Findings suggest that acoustic features that predict healthy aging are different than those previously reported for the pathologic voice. We propose a model of healthy and pathologic voice development in which voice characteristics are mediated by the inability to monitor vocal productions associated with age-related hearing loss. This normative data of healthy vocal aging may assist in separating voice pathologies from healthy aging.

Behavioral Therapy for Tremor or Dystonia Affecting Voice in Speakers with Hyperkinetic Dysarthria: A Systematic Review

INTRODUCTION

Hyperkinetic dysarthria is characterized by atypical involuntary movements within the speech mechanism that may affect the respiratory, laryngeal, pharyngeal-oral, or velopharyngeal-nasal subsystems and may alter speech production. Although articulatory impairments are commonly considered in hyperkinetic dysarthria, speakers with hyperkinetic dysarthria may also present with changes in voice quality, pitch, and loudness. In approximately 70% of speakers with hyperkinetic dysarthria, these voice alterations are associated with tremor or dystonia. The purpose of this systematic review was to investigate the association between behavioral therapy for tremor or dystonia affecting voice in speakers with hyperkinetic dysarthria and improvement in the functional, perceptual, acoustical, aerodynamic, or endoscopic characteristics of voice.

METHOD

MEDLINE (PubMed), Embase, PsycINFO, and ClinicalTrials.gov online databases were searched in August 2017, December 2018, and April 2020 for relevant studies. The searches provided 4,921 unique records, and six additional unique records were added from other sources. Twelve studies met the criteria for inclusion in the systematic review. Participants who received concurrent medical treatment were included in this review to ensure that the search was inclusive of all relevant studies and informative for typical clinical scenarios.

RESULTS

The most commonly administered treatment ingredient was relaxation training, which was investigated in three of the four studies on tremor and three of the eight studies on dystonia. Of these six studies, only one used an experimental design and administered relaxation training as the only behavioral approach. This single-case experiment reported a significant reduction in participant ratings of tremor severity and interference with activities of daily living, although the speaking subscale reportedly did not improve and oral medications were administered concurrently. In two group studies that tested potential behavioral therapy targets, production of a low pitch improved acoustical measures for participants with essential tremor and improved auditory-perceptual judgments for participants with laryngeal dystonia. Behavioral therapy improved functional, acoustical, and aerodynamic outcomes in participants with laryngeal dystonia who were also receiving botulinum toxin injections in a randomized cross-over study and a non-randomized controlled study. Because one study employed easy onset and breathing exercises, while the other employed loud voice exercises, the mechanism of action for improvement in voice associated with behavioral therapy requires further investigation.

CONCLUSION

This systematic review describes the current evidence for treatment of tremor and dystonia affecting voice in speakers with hyperkinetic dysarthria and highlights the need for future research on behavioral therapy for these disorders.

Do you have COVID-19? An artificial intelligence-based screening tool for COVID-19 using acoustic parameters

This study aimed to develop an artificial intelligence (AI)-based tool for screening COVID-19 patients based on the acoustic parameters of their voices. Twenty-five acoustic parameters were extracted from voice samples of 203 COVID-19 patients and 171 healthy individuals who produced a sustained vowel, i.e., /a/, as long as they could after a deep breath. The selected acoustic parameters were from different categories including fundamental frequency and its perturbation, harmonicity, vocal tract function, airflow sufficiency, and periodicity. After the feature extraction, different machine learning methods were tested. A leave-one-subject-out validation scheme was used to tune the hyper-parameters and record the test set results. Then the models were compared based on their accuracy, precision, recall, and F1-score. Based on accuracy (89.71%), recall (91.63%), and F1-score (90.62%), the best model was the feedforward neural network (FFNN). Its precision function (89.63%) was a bit lower than the logistic regression (90.17%). Based on these results and confusion matrices, the FFNN model was employed in the software. This screening tool could be practically used at home and public places to ensure the health of each individual's respiratory system. If there are any related abnormalities in the test taker's voice, the tool recommends that they seek a medical consultant.

Clinical Features of Essential Voice Tremor and Associations with Tremor Severity and Response to Octanoic Acid Treatment

OBJECTIVES/HYPOTHESIS

The purpose of this study was to characterize the clinical features, tremor variability, and factors related to octanoic acid (OA) treatment response in essential voice tremor (EVT).

STUDY DESIGN

Prospective, double blind, placebo-controlled, crossover study with secondary analysis.

METHODS

Clinical tremor features in 16 individuals with EVT were comprehensively assessed, and correlations with acoustic tremor severity were determined. Intrasubject and intersubject variability measures were analyzed from 18 repeated measures for each acoustic tremor variable. Clinical correlates of treatment response were evaluated, and cumulative effects over a 2-week period of OA drug dosing were assessed.

RESULTS

Participants with EVT were 90% female with a mean age of 70.31 (±8.68) years at the time of testing. Neurologist-rated body tremor beyond the vocal tract region was present in 69% of participants, and multiple vocal tract regions contributed to the voice tremor. The mean frequency of amplitude tremor was 4.67 Hz (±0.88). Respiratory tremor was evident in 50% of participants. Participants experienced moderate voice-related disability as assessed on the Voice Handicap Index-10 (19.38, ±8.50), and increased speaking effort. Acoustic tremor severity was significantly associated with severity of tremor affecting vocal tract structures. Overall intrasubject consistency was strong (single measures intraclass correlation coefficient = 0.701, P < .01), with high intersubject variability. Acoustic tremor severity was significantly, positively associated with treatment response, and results suggested a cumulative OA benefit for magnitude of amplitude tremor.

CONCLUSIONS

This study identified common clinical correlates of EVT and demonstrated positive associations between acoustic tremor severity, severity of affected vocal tract structures, and response to treatment.

LEVEL OF EVIDENCE

2 Laryngoscope, 2021.

Automatic Classification of Healthy Subjects and Patients With Essential Vocal Tremor Using Probabilistic Source-Filter Model Based Noise Robust Pitch Estimation

Essential voice tremor (EVT) is a voice disorder resulting from dyscoordination within the laryngeal musculature. A low-frequency fluctuations of fundamental voice frequency or the strength of excitation amplitude is the main consequence of the disorder. The automatic classification of healthy control and EVT is useful tool for the clinicians. A typical automatic EVT classification involves three steps. The first step is to compute the pitch contour from the speech. The second step is to compute the features from the pitch contour, and the final step is to use a classifier to classify the features into healthy or EVT. It is shown that a high-resolution pitch contour estimated from the glottal closure instants (GCIs) is useful for EVT classification. The HPRC estimation can be very poor in the presence of noise. Hence, a probabilistic source filter model based noise robust GCI detection is used for HPRC estimation. The Empirical mode decomposition based feature extraction is used followed by a support vector machine classifier. The EVT classification performance is evaluated using recordings from 45 subjects. The proposed method is found to perform better than the baseline techniques in eight different additive noise conditions with six SNR levels.

Intraoperative Evaluation of Essential Vocal Tremor in Deep Brain Stimulation Surgery

Purpose Essential vocal tremor (EVT) is a prevalent and difficult-to-manage voice disorder. There is evidence that deep brain stimulation (DBS) of the ventral intermediate nucleus (Vim) of the thalamus may be beneficial for treating EVT. The objective of this preliminary investigation was to conduct intraoperative voice assessments during Vim-DBS implantation in order to evaluate immediate voice outcomes in medication-refractory essential tremor patients with co-occurring EVT. Method Seven adult subjects diagnosed with EVT undergoing Vim-DBS surgery participated in this investigation. Voice samples of sustained vowels were collected by a speech-language pathologist preoperatively and intraoperatively, immediately following Vim-DBS electrode placement. Voice evaluation included objective acoustic assessment of the rate and extent of EVT fundamental frequency and intensity modulation and subjective perceptual ratings of EVT severity. Results The rate of intensity modulation, extent of fundamental frequency modulation, and perceptual rating of EVT severity were significantly reduced intraoperatively as compared to preoperatively. Moderate, positive correlations were appreciated between a subset of acoustic measures and perceptual severity ratings. Conclusions The results of this study demonstrate a speech-language pathologist can conduct intra-operative evaluation of EVT during DBS surgery. Using a noninvasive, simple acoustic recording method, we were able to supplement perceptual subjective observation with objective assessment and demonstrate immediate, intraoperative improvements in EVT. The findings of this analysis inform the added value of intraoperative voice evaluation in Vim-DBS patients and contribute to the growing body of literature seeking to evaluate the efficacy of DBS as a treatment for EVT.

Isolated Voice Tremor: A Clinical Variant of Essential Tremor or a Distinct Clinical Phenotype?

Background

The consensus statement by the Task Force on Tremor of the International Parkinson and Movement Disorder Society excludes individuals with "isolated voice tremor" as a clinical variant of essential tremor (ET). This clinical viewpoint presents a rationale for reconsideration of "isolated voice tremor" as a clinical variant of ET.

Methods

Evidence from the literature was extracted to characterize the clinical phenotype of "isolated voice tremor," or essential vocal tremor (EVT). Clinical features were extracted from relevant literature available at pubmed.gov using the terms "EVT," "essential voice tremor," "primary voice tremor," and "organic voice tremor."

Results

The average age of onset in those with EVT was older than 60 years (range 19-84 years), with 75-93% being female. The typical duration of vocal tremor ranged from 1 to 13 years (average 6 years). The distribution of structures exhibiting tremor included the larynx, soft palate, pharynx, and base of tongue in the majority of patients, with some exhibiting tremor of the head and respiratory musculature. The condition of tremor occurred during speech and quiet respiration in 74% of individuals. Rate of tremor ranged from 4 to 10 Hz. Nearly 70% reported onset of vocal tremor prior to upper limb involvement. Family history of tremor was reported in 38-42% of individuals.

Discussion

Those previously classified with EVT demonstrate a similar familial history, rate, tremor classification, and body distribution of ET. EVT is proposed as a clinical variant of ET in the pattern of onset and progression of body distribution from the midline cranial to spinal neural pathways.

Objective Acoustic Quantification of Perceived Voice Tremor Severity

Purpose This study compared auditory-perceptual measures of presence/absence and severity of vocal tremor to acoustic markers of vocal tremor. The validity (both concurrent and diagnostic) of various acoustic markers of vocal tremor was also assessed. Method Fifty-six midvowel sustained [a:] recordings were selected to yield a representative convenience sample of vocal tremor. After training with 10 synthesized samples, 4 female audiologists rated these samples on "voice tremor severity" on a continuous 10-cm scale. Afterward, 15 randomly selected recordings were presented a 2nd time for intrarater reliability assessment. Customized audio signal processing in Praat yielded 12 acoustic measures of rate, extent and perturbation of fundamental frequency (f ₀), and intensity level (IL) modulation. Enter-type multiple linear regression analysis was applied to weight and combine these acoustic variables into an acoustic model of vocal tremor severity. Results After removing the vocal tremor severity ratings of 1 of the audiologists because of insufficient intra- and interrater reliability, mean single-measures consistency-type intraclass correlation coefficients equaled .83 within raters and .72 between raters. Correlation between mean ratings and the 12 acoustic markers ranged from .76 for median extent of f ₀ modulation to .11 for rate of IL modulation. Correlation between mean ratings and the acoustic model was .89. Analysis of this model's receiver operating characteristics yielded an area under receiver operating characteristic curve of .93, denoting sensitivity of .87 and specificity of .91. Conclusions This study demonstrated that auditory-perceptual ratings of vocal tremor severity are guided primarily by f ₀ and IL modulation extent, less by modulation perturbation, and least by modulation rate. The acoustic model covering all these modulation properties yielded acceptable results in terms of both concurrent and diagnostic validity. However, external cross-validation of this model is warranted before applying it in clinical voice/speech assessment.

The Effect of Octanoic Acid on Essential Voice Tremor: A Double-Blind, Placebo-Controlled Study

OBJECTIVES/HYPOTHESIS

The purpose of this study was to determine the effects of octanoic acid on acoustic, perceptual, and functional aspects of essential voice tremor (EVT).

STUDY DESIGN

Prospective, double-blind, placebo-controlled, crossover study.

METHODS

Sixteen participants with a diagnosis of EVT were randomized to a 3-week dosing condition of octanoic acid or placebo, followed by a 2-week washout period and crossover to the other condition for an additional 3 weeks. Baseline and post-testing sessions were completed before and at the completion of each condition. Primary outcome measures were the magnitude of amplitude and frequency tremor, measured from the acoustic signal. Secondary outcomes were auditory-perceptual ratings of tremor severity and self-ratings of voice handicap.

RESULTS

Magnitude of amplitude and frequency tremor were significantly lower after 3 weeks of octanoic acid dosing as compared to the placebo condition. Auditory-perceptual ratings of tremor severity did not show significant differences between conditions. A trend toward better voice was seen for the sustained vowel ratings, but not the sentence-level ratings. No significant differences between conditions were seen on self-reported voice disability as assessed on the Voice Handicap Index-10.

CONCLUSIONS

The results of this controlled investigation support the potential utility of octanoic acid for reducing the magnitude of tremor in people with EVT. Further research is needed to determine whether different dosing or treatment combinations can improve functional communication in EVT.

LEVEL OF EVIDENCE

1 Laryngoscope, 129:1882-1890, 2019.

The effects of physiological adjustments on the perceptual and acoustical characteristics of vibrato as a model of vocal tremor

The purpose of this study was to investigate the effects of physiological adjustments on listeners' perception of the magnitude of modulation of voice and to determine the characteristics of the acoustical modulations that explained listeners' judgments. This research was carried out using singers producing vibrato as a model of vocal tremor. Twenty healthy adults participated in a perceptual study involving pair-comparisons of the magnitude of "shakiness" with singers' samples, which differed by fundamental frequency, vocal quality, and vowel. Results revealed that listeners perceived a higher magnitude of voice modulation when female samples had a pressed vocal quality. Acoustical analyses were performed with voice samples to determine the features that predicted listeners' judgments. Based on regression analyses, listeners' judgments were predicted to some extent by modulation information in frequency bands across the spectrum.

The effects of physiological adjustments on the perceptual and acoustical characteristics of simulated laryngeal vocal tremor

The purpose of this study was to determine if adjustments to the voice source [i.e., fundamental frequency (F0), degree of vocal fold adduction] or vocal tract filter (i.e., vocal tract shape for vowels) reduce the perception of simulated laryngeal vocal tremor and to determine if listener perception could be explained by characteristics of the acoustical modulations. This research was carried out using a computational model of speech production that allowed for precise control and manipulation of the glottal and vocal tract configurations. Forty-two healthy adults participated in a perceptual study involving pair-comparisons of the magnitude of "shakiness" with simulated samples of laryngeal vocal tremor. Results revealed that listeners perceived a higher magnitude of voice modulation when simulated samples had a higher mean F0, greater degree of vocal fold adduction, and vocal tract shape for /i/ vs /ɑ/. However, the effect of F0 was significant only when glottal noise was not present in the acoustic signal. Acoustical analyses were performed with the simulated samples to determine the features that affected listeners' judgments. Based on regression analyses, listeners' judgments were predicted to some extent by modulation information present in both low and high frequency bands.

Discriminating simulated vocal tremor source using amplitude modulation spectra

OBJECTIVES/HYPOTHESIS

Sources of vocal tremor are difficult to categorize perceptually and acoustically. This article describes a preliminary attempt to discriminate vocal tremor sources through the use of spectral measures of the amplitude envelope. The hypothesis is that different vocal tremor sources are associated with distinct patterns of acoustic amplitude modulations.

STUDY DESIGN

Statistical categorization methods (discriminant function analysis) were used to discriminate signals from simulated vocal tremor with different sources using only acoustic measures derived from the amplitude envelopes.

METHODS

Simulations of vocal tremor were created by modulating parameters of a vocal fold model corresponding to oscillations of respiratory driving pressure (respiratory tremor), degree of vocal fold adduction (adductory tremor), and fundamental frequency of vocal fold vibration (F0 tremor). The acoustic measures were based on spectral analyses of the amplitude envelope computed across the entire signal and within select frequency bands.

RESULTS

The signals could be categorized (with accuracy well above chance) in terms of the simulated tremor source using only measures of the amplitude envelope spectrum even when multiple sources of tremor were included.

CONCLUSIONS

These results supply initial support for an amplitude-envelope-based approach to identify the source of vocal tremor and provide further evidence for the rich information about talker characteristics present in the temporal structure of the amplitude envelope.

Updates on Vocal Tremor and its Management

Vocal tremor is a neurogenic voice disorder characterized by a nearly periodic modulation in pitch and loudness during sustained phonation. This voicing pattern is the result of tremor affecting structures within the speech mechanism, resulting in modulation of lung pressure, phonation, articulation, and resonance during speaking. Speaking patterns in these individuals may be perceived as similar to spasmodic dysphonia or muscle tension dysphonia. The key to determining the presence of vocal tremor and distinguishing it from other voice disorders requires familiarity with the perceptual, acoustic, and physiologic patterns associated with vocal tremor during different voicing and speech contexts. Management of those with vocal tremor can be challenging because of its co-occurrence with other neurological disorders. The two most common methods for managing vocal tremor include pharmaceutical treatment, most commonly applied via injections of Botulinum Toxin Type A (Botox®), and behavioral modification of speaking patterns. The latter approach is in early clinical phases of research and has not yet been subjected to clinical trials. In this paper, I will summarize the clinical characteristics of vocal tremor in comparison to what is known about tremor in general and describe Botox® and behavioral approaches for managing individuals with this voice disorder.

Reflexive and volitional voice fundamental frequency responses to an anticipated feedback pitch error

The pitch-shift reflex is a corrective voice fundamental frequency (F0) response triggered by a sudden shift or "error" in auditory feedback pitch. We investigated how anticipating a voice pitch error affects the pitch-shift reflex and volitional voice F0 responses. Adults sustained the vowel/u/at a comfortable pitch and pressed a button to deliver a 100 cent, 100 ms auditory feedback pitch shift immediately or after a random delay. Pitch shift direction was either constant (up) or randomized (up or down). Onset anticipation often resulted in an anticipatory voice F0 change, but stimulus direction predictability did not affect the responses. When pitch error onset and direction were both anticipated, some participants produced an ideomotor voice F0 change that partially imitated the error, but they produced no apparent pitch-shift reflex. Results imply that when voice pitch errors are anticipated, volitional voice F0 responses may reduce or enhance voice F0 stability.

Vocal tremor and vibrato in the same person: acoustic and electromyographic differences

The goal of this case study was to measure and describe differences between vocal vibrato and essential tremor of the voice in one individual who exhibited both types of modulation. Recordings of spoken and sung vowels produced by the same individual at three effort levels were examined via analysis of acoustic and laryngeal electromyographic (LEMG) signals. Modulation rate, periodicity, and spectral measures of both audio and muscle activation signals revealed generally slower, more prominent, and more regular patterns in sung than in spoken conditions. There was not always a clear correspondence between LEMG and acoustic measures, but both showed differences between the vibrato and tremor of this individual, suggesting differences in the neural bases of these modulations.

Listener perception of respiratory-induced voice tremor

PURPOSE

The purpose of this study was to determine the relation of respiratory oscillation to the perception of voice tremor.

METHOD

Forced oscillation of the respiratory system was used to simulate variations in alveolar pressure such as are characteristic of voice tremor of respiratory origin. Five healthy men served as speakers, and 6 clinically experienced women served as listeners. Speakers produced utterances while forced sinusoidal pressure changes were applied to the surface of the respiratory system. Utterances included vowels and sentences produced using usual loudness, pitch, quality, and rate, and vowels produced using different loudness, pitch, and quality. Perceptual tasks included detection threshold for voice tremor and pair comparison judgments in which listeners identified the sample with the greater magnitude of voice tremor.

RESULTS

The mean detection threshold for voice tremor was 1.37 cmH(2)O (SD = 0.47) for vowel utterances and 2.16 cmH(2)O (SD = 1.52) for sentence utterances. Tremor magnitude was judged to be different for vowel and sentence utterances, but not for different vowels. Results revealed differential effects for loudness, pitch, and quality.

CONCLUSIONS

These findings offer implications for the evaluation and management of voice tremor of respiratory causation.