“Compensatory falsetto”: Effects on vocal quality

The term “compensatory falsetto”, for the purpose of this investigation, refers to the development of an abnormally high-pitched voice in the presence of laryngeal pathology where more socially acceptable lower pitched voice production is possible. The purpose of this investigation was to compare laryngeal compensations and their effects on objective measures of vocal function during production of compensatory falsetto voice. Eighteen patients with abnormally high-pitched voice in the presence of underlying laryngeal pathology were evaluated in the Department of Otolaryngology at the University of Miami School of Medicine from January 1988 through December 1992 and were diagnosed with “compensatory falsetto”. Vocal fold paralysis (n = 11) was the most common laryngeal pathology. Vibratory characteristics were evaluated through videostrobolaryngoscopic examination. Acoustic and aerodynamic parameters assessed included fundamental frequency, jitter rate, harmonic-to-noise ratio, glottal air flow, and maximum phonation time. Production of a higher-pitched voice appeared to improve glottic closure and decrease the amount of air loss during phonation. A corresponding increase in maximum phonation time and improvement in acoustic characteristics of jitter and harmonic-to-noise ratio was also observed.     

Effects of laryngeal endoscopy on the vocal performanceof young adult females with normal voices

This study investigated changes in maximum phonation time andacoustic and perceptual measures of voice following topical anesthesia and laryngeal endoscopy with the flexible endoscope. Forty-four females, aged 18–33 years and with normal voices, performed four vocal tasks: (a) 3-second /i/ prolongation, (b) maximum phonation time on /i/, (c) stepwise scale-singing, and (d) reading a standard passage. Subjects performed these tasks prior to anesthesia, after anesthesia, and again during laryngeal endoscopy. Voice samples were analyzed for jitter, shimmer, harmonic-to-noise ratio, speaking fundamental frequency, maximum phonational frequency range, maximum phonation time, harshness, and breathiness. Results demonstrated significant reductions in maximum phonational frequency range following anesthesia and, during laryngeal endoscopy, reductions in maximum phonation time and increases in speaking fundamental frequency, minimum fundamental frequency on scale-singing, and breathiness. Clinicians using laryngeal endoscopy for evaluation and management of vocal dysfunction should, therefore, consider the possible effects of these procedures on vocal functioning.     

Vocal Warm-up Increases Phonation Threshold Pressure in Soprano Singers at High Pitch

Vocal warm-up is thought to optimize singing performance. We compared effects of short-term, submaximal, vocal warm-up exercise with those of vocal rest on the soprano voice (n = 10, ages 19-21 years). Dependent variables were the minimum subglottic air pressure required for vocal fold oscillation to occur (phonation threshold pressure, Pth), and the maximum and minimum phonation fundamental frequency. Warm-up increased Pth for high pitch phonation (p = 0.033), but not for comfortable (p = 0.297) or low (p = 0.087) pitch phonation. No significant difference in the maximum phonation frequency (p = 0.193) or minimum frequency (p = 0.222) was observed. An elevated Pth at controlled high pitch, but an unchanging maximum and minimum frequency production suggests that short-term vocal exercise may increase the viscosity of the vocal fold and thus serve to stabilize the high voice.     

Aerodynamic measurements of patients with parkinson''s disease

Patients with Parkinson's disease commonly complain of voice dysfunction. Most of these complaints can be attributed to the known muscular control disorders that occur with Parkinson's disease. However, the manifestations of Parkinson's disease muscular dysfunction on parameters of phonation such as airflow, laryngeal resistance, and subglottal pressure necessary to sustain phonation have not been reported. The purpose of this study was to examine the aerodynamic characteristics of flow, laryngeal resistance, and phonation pressure threshold in a heterogeneous population of patients with Parkinson's disease who had varying voice complaints and to compare the data to similar studies for human subjects who have no voice complaints. The studies used a noninvasive method of detecting flow and acoustic signal from the lips, oral cavity and nose during phonation and used an external flow interruption technique to estimate subglottal pressure and phonation threshold pressure. About one third of the patients could not produce phonation at regular and loud intensities that were comfortable for normal subjects. The mean subglottal pressure (SGP) of patients with Parkinson disease who could produce 3 levels of intensity comparable to normal subjects was significantly higher than the mean SG-Ps for normal subjects for the same intensities of vocal production. The mean flow rates measured from patients with Parkinson's disease at the same 3 intensities of phonation was not significantly greater than in normal subjects. This indicated that the mean laryngeal resistance calculated for patients with Parkinson's disease was notably and significantly greater than mean laryngeal resistance calculated for normal subjects at the same intensity levels. The mean vocal efficiency (VE) for normal subjects was not significantly different than the mean VE for patients with Parkinson's disease, because greater pressure was used to generate similar flow and acoustic energy. These findings correlate with the perception of patients with Parkinson's disease that they are working harder to produce phonation. The observation of notably greater laryngeal resistance and phonation threshold pressure in patients with Parkinson's disease suggests that further studies of the glottic aperture in patients with Parkinson' disease may be useful for understanding how this common motor disorder disturbs phonation.     

Analysis of Voice and Quantitative Measurement of Glottal Gap After Thyroplasty Type I in the Treatment of Unilateral Vocal Paralysis

Thyroplasty type I is one of several surgical treatments in which improving the voice of unilateral vocal fold paralysis is the ultimate objective. The goal of the surgery is the medialization of the paralyzed vocal fold. The purpose of this study is to evaluate the effectiveness of thyroplasty type I through acoustical analysis, aerodynamic measures, and quantitative videostroboscopic measurements. We report on 20 patients with unilateral vocal cord paralysis who underwent thyroplasty type I. We performed preoperative and postoperative video image analysis (normalized glottal gap area) and computer-assisted voice analysis (fundamental frequency, jitter, shimmer, noise-to-harmonic ratio, mean phonation time, mean flow rate, mean subglottic pressure) in all patients. The glottal gap was significantly reduced after thyroplasty type I. Postoperative voice quality was characterized by an improved pitch and amplitude pertubation (jitter and shimmer), phonation time (mean phonation time), and subglottic pressure (mean subglottic pressure). Thyroplasty type I is an effective method for regaining glottal closure and vocal function.     

The role of strap muscles in phonation—In vivo caninelaryngeal model

In spite of the presumed importance of the strap muscles on laryngealvalving and speech production, there is little research concerning the physiological role and the functional differences among the strap muscles. Generally, the strap muscles have been shown to cause a decrease in the fundamental frequency (F₀) of phonation during contraction. In this study, an in vivo canine laryngeal model was used to show the effects of strap muscles on the laryngeal function by measuring the F₀, subglottic pressure, vocal intensity, vocal fold length, cricothyroid distance, and vertical laryngeal movement. Results demonstrated that the contraction of sternohyoid and sternothyroid muscles corresponded to a rise in subglottic pressure, shortened cricothyroid distance, lengthened vocal fold, and raised F₀ and vocal intensity. The thyrohyoid muscle corresponded to lowered subglottic pressure, widened cricothyroid distance, shortened vocal fold, and lowered F₀ and vocal intensity. We postulate that the mechanism of altering F₀ and other variables after stimulation of the strap muscles is due to the effects of laryngotracheal pulling, upward or downward, and laryngotracheal forward bending, by the external forces during strap muscle contraction.     

Vocal loudness and frequency capabilities of the voice

A phonetogram is a graph showing the sound pressure level (SPL) of softest and loudest phonation over the entire fundamental frequency range of a voice. A physiological interpretation of a phonetogram is facilitated if the SPL is measured with a flat frequency curve and if the vowel /a/ is used. It was found that in soft phonation, the SPL is mainly dependent on the amplitude of the fundamental, while in loud phonation, the SPL is mainly determined by overtones. The short-term SPL variation, i.e., the level variation within a tone, was about 5 dB in soft phonation and close to 2 dB in loud phonation. For two normal voices the long-term SPL variation, calculated as the mean standard deviation of SPL for day-to-day variation, was found to be between 2.4 and 3.4 dB in soft and loud phonation. Speakers who raise their loudness of phonation also tend to raise their mean voice fundamental frequency. Measures obtained from speaking at various voice levels were combined so that typical pathways could be introduced into the phonetogram. The average slope of these pathways was 0.3–0.5 st/dB for healthy subjects. Averaged phonetograms for male singers and male nonsingers did not differ significantly, but averaged phonetograms for female singers and female nonsingers did, in that the upper contour was higher for the female singers. Averaged phonetograms for female patients with non-organic dysphonia showed significantly lower SPL values in loudest phonation as compared to healthy female subjects, while no corresponding difference was seen for males in this regard. With respect to the SPL values for softest phonation, male dysphonic patients showed significantly higher SPL values than healthy male subjects, while no corresponding difference was seen in female subjects. The subglottal pressure mirrored these phonetogram differences between healthy and pathological voices. The averaged phonetograms of female patients after voice therapy showed an increased similarity with those of normal voices. For the male patients the averaged phonetogram did not change significantly after therapy.     

Fundamental Frequency Change During Offset and Onset of Voicing in Individuals with Parkinson Disease

SUMMARY: After years of treatment with the medication levodopa, most individuals with Parkinson disease (PD) experience fluctuations in response to their medications. Although relatively consistent perceptual voice improvements have been documented to correspond with these fluctuations, consistent quantitative data to support this finding are lacking. This mismatch may have occurred because most of this phonation research has centered on long-term phonatory measures (ie, across speaking samples and prolonged vowel tasks). The current study examined short-term phonatory behavior in individuals with PD, specifically examining fundamental frequency (F0) at the offset and onset of phonation, before and after a voiceless consonant. The F0 analysis at phonatory offset supported the conclusion that individuals with PD have difficulty with the rapid offset of voicing, and that they are stopping vocal fold vibration primarily through vocal fold abduction (without adding tension). The F0 analysis at phonatory onset revealed that all groups use some laryngeal tension at the initiation of voicing. The tension was lowest for the PD participants who were in their OFF medication state, and it was highest for the age-matched control participants and the PD participants in their ON medication states.     

Consistency of acoustic and aerodynamic measures of voice production over 28 days under various testing conditions

The value of any measure of voice production is dependent on its repeatability over time. The purpose of the present study was to determine the consistency of selected acoustic and aerodynamic measures of voice production over 28 days, under various test/retest conditions. Three groups of healthy young adult females sustained three vowels at comfortable, high, and low pitch levels. Subjects in Group 1 chose their own intensity levels, but matched the fundamental frequencies produced at Test 1 during Test 2. Group 2 controlled intensity levels during both tests, but fundamental frequency was free to vary. Group 3 controlled both intensity and fundamental frequency. Measures of fundamental frequency, jitter, maximum phonation time, phonation volume, and flow rate were compared. Subjects who matched both fundamental frequency and intensity showed repeatable, consistent results for all measures during both tests. Controlling intensity but not fundamental frequency resulted in statistically significant differences in fundamental frequency at comfortable and high pitches, but there was minimal effect on other variables. Controlling fundamental frequency but not intensity led to the most inconsistency between tests, affecting both acoustic and aerodynamic measures. Results underscore the need to control the conditions under which measures are obtained.     

Direct measurement of onset and offset phonation threshold pressure in normal subjects

Phonation threshold pressures were directly measured in five normal subjects in a variety of voicing conditions. The effects of fundamental frequency, intensity, closure speed of the vocal folds, and laryngeal airway resistance on phonation threshold pressures were determined. Subglottic air pressures were measured using percutaneous puncture of the cricothyroid membrane. Both onset and offset of phonation were studied to see if a hysteresis effect produced lower offset pressures than onset pressures. Univariate analysis showed that phonation threshold pressure was influenced most strongly by fundamental frequency and intensity. Multiple linear regression showed that these two variables, as well as laryngeal airway resistance, most strongly predicted phonation threshold pressure. Two of the five subjects demonstrated a significant hysteresis effect, but one subject actually had higher offset pressures than onset pressures.     

Problems and pitfalls of electroglottography

The popularity and usefulness of the electroglottograph (EGG) has increased remarkably since its introduction over a decade ago. It has been used to measure fundamental frequency of phonation, fundamental frequency perturbation, details of the vocal fold vibratory cycle, as well as to provide an indication of laryngeal vertical movement. It has also been used with a variety of speech and voice disorders. The EGG is not without its limitations and problems. Some of these are found in the electronic designs of specific instruments, whereas other problems are related to subject characteristics, the placement of the electrodes, electrode symmetry, and subject/instrument interaction. This article explores some of these concerns, primarily from the perspective of two individuals who have used the EGG extensively with children, men and women, voice patients, stutterers, and neurologically impaired persons. Some of the concerns to consider and pitfalls to avoid in the interpretation and measurement of EGG signal are discussed.     

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 (SPL_max) 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.     

Effect of Fasting on Voice in Women

OBJECTIVE/HYPOTHESIS: To study the effect of fasting on voice in women: abstinence from food and water intake between 14 and 18 hours. STUDY DESIGN: A prospective study on female subjects. MATERIAL AND METHOD: A total of 28 female subjects were included in this study. Their age ranged between 21 and 45 years. Subjects with vocal symptoms or vocal fold lesions were excluded. The subjects were tested when they were not fasting and while fasting after the first week of intermittent fasting during Ramadan. Each subject was first asked about her vocal symptoms and the ease of phonation or phonatory effort. Then each underwent acoustic analysis and laryngeal video-endostroboscopy. RESULTS: Vocal fatigue was the most common reported complaint (53.6%) followed by deepening of the voice (21.4%) and harshness (10.2%). Self-reported phonatory effort was significantly affected by fasting (P value < 0.001). Out of the 28 subjects, 23 had an increase in their phonatory effort. Vocal acoustic parameters did not change markedly except for the maximum phonation time, which decreased significantly. Laryngeal video-endostroboscopy did not reveal any significant changes during fasting. All stroboscopic parameters were the same except for a decrease in the amplitude of the mucosal waves in one subject and the presence of a posterior chink in three subjects. CONCLUSION: Fasting affects voice. There is an increase in the phonatory effort, and vocal fatigue is the most common symptom.     

Objective Voice Measures in Nonsinging Patients With Unilateral Superior Laryngeal Nerve Paresis

The clinical value of objective voice measures in nonsinging patients with superior laryngeal nerve dysfunction is unknown. In this study, patients with symptomatic unilateral superior nerve paresis were evaluated for maximum phonation time, frequency range of phonation, and mean flow rate. Patients with coexisting pathology, bilateral superior nerve paresis, and those with recurrent laryngeal nerve paresis were excluded from this analysis. A total of 35 nonsinging patients, 14 men and 21 women, with unilateral superior laryngeal nerve paresis were examined between 1999 and 2002. The severity of superior laryngeal nerve paresis ranged from 25% to 85% of normal recruitment with a mean of 70% superior laryngeal nerve recruitment in men and 65% in women by electromyography. In both men and women with superior laryngeal nerve paresis, the maximum phonation time and frequency range of phonation were decreased and the mean air flow rate was increased when compared with normal population values. The jitter percent, shimmer percent, and noise-to-harmonic ratio were also increased in patients when compared with normative data. Selected objective voice measures are abnormal in voice patients with superior laryngeal nerve paresis, which suggests that the measures may be useful as outcomes measures after therapy. More research is encouraged.     

Model-based classification of nonstationary vocal fold vibrations

Classification of vocal fold vibrations is an essential task of the objective assessment of voice disorders. For historical reasons, the conventional clinical examination of vocal fold vibrations is done during stationary, sustained phonation. However, the conclusions drawn from a stationary phonation are restricted to the observed steady-state vocal fold vibrations and cannot be generalized to voice mechanisms during running speech. This study addresses the approach of classifying real-time recordings of vocal fold oscillations during a nonstationary phonation paradigm in the form of a pitch raise. The classification is based on asymmetry measures derived from a time-dependent biomechanical two-mass model of the vocal folds which is adapted to observed vocal fold motion curves with an optimization procedure. After verification of the algorithm performance the method was applied to clinical problems. Recordings of ten subjects with normal voice and ten dysphonic subjects have been evaluated during stationary as well as nonstationary phonation. In the case of nonstationary phonation the model-based classification into "normal" and "dysphonic" succeeds in all cases, while it fails in the case of sustained phonation. The nonstationary vocal fold vibrations contain additional information about vocal fold irregularities, which are needed for an objective interpretation and classification of voice disorders.     

Control of Fundamental Frequency in Dysphonic Patients During Phonation and Speech

PurposeThe pitch-shift reflex (PSR) is the adaptation of the fundamental frequency during phonation and speech and describes the auditory feedback control. Speakers without voice and speech disorders mostly show a compensation of the pitch change in the auditory feedback and adapt their fundamental frequency to the opposite direction. Dysphonic patients often display problems with the auditory perception and control of their voice during therapy. Our study focuses on the auditory and kinesthetic control mechanisms of patients with muscle tension dysphonia (MTD) and speakers without voice and speech problems. Main purpose of the study is the analysis of the functionality of the control mechanisms within phonation and speech between patients with MTD and normal speakers.MethodSixty-one healthy subjects (17 male, 44 female) and 22 patients with MTD (7 male, 15 female) participated following two paradigms including a sustained phonation (vowel /a/) and speech ([‘mama]). Within both paradigms the fundamental frequency of the auditory feedback was increased synthetically. For the analysis of the PSR the electroencephalogram, electroglottography, the voice signal, and the high-speed endoscopy data were recorded simultaneously. The PSR in the electroencephalogram was detected via the N100 and the mismatch negativity. Statistical tests were applied for the detection of the PSR in the physiological response within the electroglottography, voice, and high-speed endoscopy signals. The results were compared between both groups.ResultsNo differences were found between the controls and patients with MTD regarding latency and magnitude of the perception of the pitch shift in both paradigms, but for the magnitude of the behavioral response. Differences also could be found for both groups between the “no pitch” and “pitch” condition of the two paradigms regarding vocal fold dynamics and voice quality. Patients with MTD showed more vibrational irregularities during the PSR than the controls, especially regarding the symmetry of vocal fold dynamics.ConclusionPatients with MTD seem to have a disturbed interaction between the auditory and kinesthetic feedback inducing the execution of an overriding behavioral response.     

Observation and analysis of in vivo vocal fold tissue instabilities produced by nonlinear source-filter coupling: a case study

Different source-related factors can lead to vocal fold instabilities and bifurcations referred to as voice breaks. Nonlinear coupling in phonation suggests that changes in acoustic loading can also be responsible for this unstable behavior. However, no in vivo visualization of tissue motion during these acoustically induced instabilities has been reported. Simultaneous recordings of laryngeal high-speed videoendoscopy, acoustics, aerodynamics, electroglottography, and neck skin acceleration are obtained from a participant consistently exhibiting voice breaks during pitch glide maneuvers. Results suggest that acoustically induced and source-induced instabilities can be distinguished at the tissue level. Differences in vibratory patterns are described through kymography and phonovibrography; measures of glottal area, open/speed quotient, and amplitude/phase asymmetry; and empirical orthogonal function decomposition. Acoustically induced tissue instabilities appear abruptly and exhibit irregular vocal fold motion after the bifurcation point, whereas source-induced ones show a smoother transition. These observations are also reflected in the acoustic and acceleration signals. Added aperiodicity is observed after the acoustically induced break, and harmonic changes appear prior to the bifurcation for the source-induced break. Both types of breaks appear to be subcritical bifurcations due to the presence of hysteresis and amplitude changes after the frequency jumps. These results are consistent with previous studies and the nonlinear source-filter coupling theory.     

Measures of phonation type in Hmong

This study examines measures of glottal flow for vowels of Hmong, a Southeast Asian language which uses breathy and normal phonation contrastively. A software inverse filter was used to recover glottal airflow from oral airflow recordings. Properties of glottal flow measured in the time domain were glottal pulse symmetry and relative closed-phase duration. In the frequency domain, measures of spectral tilt and the amplitude difference between F0 and H2 were applied to discrete Fourier transforms (DFTs) of the glottal flow waveforms. Spectral tilt could not be reliably measured for many tokens. For the other measures, values were available for all tokens and were compared across phonation types. Flow pulse symmetry is not significantly different for breathy and normal-voice vowels. On the other hand, prominence of the fundamental relative to the second harmonic is a very significant correlate of the breathy/normal distinction, as is the relative closed-phase duration. These results are considered in light of an existing model of the voice source.