Vocal Instability Research Articles

Ataxia espinocerebelar: análise perceptivo-auditiva e acústica da fala em três casos

dysarthrias are commonly found in patients with spinocerebellar ataxias (SCA). to characterize perceptual and acoustic features of speech in three patients with spinocerebellar ataxia and to verify the presence of similar features among these patients. speech samples of two males with SCA3 and one male with SCA2 were obtained. Both perceptual and acoustic analyses were done. It was observed strain-strangled and breathiness phonation, vocal instability, increased noise-to-harmonics ratio and low alternate motion rate (AMR) and speech rate in all three patients. Deviated resonance and s/z ratio were also observed. phonatory disorders and altered temporal patterns of speech seem to be typical in dysarthric patients with spinocerebellar ataxia.

Not just sound: Supplementing the voice range profile with the singer's own perceptions of vocal challenges

A commercial phonetograph was complemented with a response button, such that presses resulted in marked regions in the voice range profile (VRP). This study reports the VRP data of 16 healthy female professionally trained singers (7 mezzo-sopranos and 9 sopranos). Subjects pressed the button to indicate sensations of vocal instability or reduced control during phonation. Each press thereby marked potential areas of difficulty. A method is presented to quantify the consistency of button use for repeated tasks. The pattern of button presses was significantly consistent within subjects. As expected, the singers pressed at the extremes of VRP contours as well as at register transitions. These results and the potential of the method for the assessment of vocal problems of singers are discussed.

Perceptual and acoustic analysis of speech in individuals with spinocerebellar ataxia (SCA)

With current progress in genetic research, autosomal, dominant, hereditary, neurodegenerative diseases, affecting the cerebellum and cerebellar connections, are increasingly diagnosed as spinocerebellar ataxias (SCA). In the present study speech samples from 21 subjects with spinocerebellar ataxia (SCA), and 21 matched control subjects were analyzed using perceptual and acoustic methodology. Dysarthria assessment showed that subjects had mild or mild-moderate dysarthria. Perceptual analysis indicated that equalized stress, imprecise consonants, vocal instability, monotony and reduced speech rate were the speech parameters that yielded the highest mean perceptual ratings. A factor analysis of perceptual speech parameters revealed two main factors: Factor 1 was associated with articulatory timing and Factor 2 with vocal quality. Acoustic analysis revealed significantly reduced speech rate during text reading, reduced alternating and sequential motion rates (AMR/SMR), significantly longer and more variable syllable and pause durations, and significantly higher vocal instability for subjects with SCA compared to control subjects.

Acoustic Analysis of Speech Tasks Performed by Three Individuals with Spinocerebellar Ataxia

A number of speech tasks produced by three female subjects with different types of genetically diagnosed spinocerebellar ataxia and with mild dysarthria were investigated using acoustic instrumentation. All subjects showed a number of signs of decreased speech rate, increased pause duration, increased and more variable durations of alternating motion rate, sequential motion rate syllables and inter-stress intervals in addition to vocal instability. These signs were consistent with the perceptual judgment of ataxic dysarthria. Furthermore, the severity of impairment found using these speech analysis methods seemed to correspond to the general severity of the disease and the duration of the illness in these few subjects. The tasks studied appeared to be relevant and suitable for acoustic analyses as they did reveal deviations in the speech of the subjects compared with controls.

Vocal stability in functional dysphonic versus healthy voices at different times of voice loading

Summary Functional (nonorganic) dysphonia is often characterized by vocal instability. The purpose of the prospective study was to examine whether there is a difference in vocal instability of functional dysphonic voices compared with healthy ones, this means whether electroglottographic perturbation values differ (1) between healthy and dysphonic voices and (2) between two subgroups of the dysphponic voices (hpertonic and hypotonic dysphonic voices). Twenty-three patients with hypertonic functional dysphonia, 9 with hypotonic functional dysphonia and 31 healthy nonsmokers, were each examined electroglottographically before (Ex 1), immediately after (Ex 2), and 1 hour after (Ex 3) voice loading. Perturbations of frequency, amplitude, quasi-open-quotient, and contact-index were calculated from the EGG signal. At all three times of examination, hypertonic dysphonic voices showed higher perturbations than healthy voices, and they had higher perturbations than hypotonic dysphonic voices before and 1 hour after voice loading. Hypotonic dysphonic voices showed higher perturbations than healthy voices only 1 hour after voice loading. Voice loading induced different reactions in dysphonic voices: Some voices showed increased perturbations, and others exhibited normal or even decreased perturbation immediately after voice loading. Examination of electroglottographic-derived perturbations immediately after voice loading seems not to be useful. Differentiation of hypertonic and hypotonic dysphonic voices was possible with an estimated sensitivity of 88.9% and a specificity of 87.0% by using the sum of the amplitude-perturbation and the quasi-open-quotient-perturbation measured before voice loading.

Estudo do comportamento vocal no ciclo menstrual: avaliação perceptivo-auditiva, acústica e auto-perceptiva

Durante o período pré-menstrual é comum a ocorrência de disfonia, e são poucas as mulheres que se dão conta dessa variação da voz dentro do ciclo menstrual (Quinteiro, 1989). OBJETIVO: Verificar se há diferença no padrão vocal de mulheres no período de ovulação em relação ao primeiro dia do ciclo menstrual, utilizando-se da análise perceptivo-auditiva, da espectrografia, dos parâmetros acústicos e quando esta diferença está presente, se é percebida pelas mulheres. FORMA DE ESTUDO: Caso-controle. MATERIAL E MÉTODO: A amostra coletada foi de 30 estudantes de Fonoaudiologia, na faixa etária de 18 a 25 anos, não-fumantes, com ciclo menstrual regular e sem o uso de contraceptivo oral. As vozes foram gravadas no primeiro dia de menstruação e no décimo-terceiro dia pós-menstruação (ovulação), para posterior comparação. RESULTADOS: Observou-se durante o período menstrual que as vozes estão rouco-soprosa de grau leve a moderado, instáveis, sem a presença de quebra de sonoridade, com pitch e loudness adequados e ressonância equilibrada. Há pior qualidade de definição dos harmônicos, maior quantidade de ruído entre eles e menor extensão dos harmônicos superiores. Encontramos uma f0 mais aguda, jitter e shimmer aumentados e PHR diminuída. CONCLUSÃO: No período menstrual há mudanças na qualidade vocal, no comportamento dos harmônicos e nos parâmetros vocais (f0,jitter, shimmer e PHR). Além disso, a maioria das estudantes de Fonoaudiologia não percebeu a variação da voz durante o ciclo menstrual.

Improvements in methodology for the pitch-shifting technique

In recent years several studies have been published on voice control that utilized the pitch-shifting technique. The technique requires averaging of multiple vocalizations to repeated presentations of pitch-shifted feedback in order to eliminate random fluctuations in voice fundamental frequency. Time-locked reflexive responses to a stimulus parameter are observed quite clearly after averaging. The present study was undertaken to improve the pitch-shift methodology for data acquisition and analysis. Auditory pitch stimuli were presented at rates of 10, 5, and 2 per 5-sec vocalization, as opposed to previous studies that used one stimulus per vocalization. Results of testing these rates of stimulus presentation on a group of 22 subjects indicated there was no difference in reflex magnitude or latency between the present methods and rates up to 5/vocalization. Rates of 10/vocalization led to a reduction in reflex magnitude. Using the 5/vocalization rate, it was possible to reduce the number of vocalizations required of each subject per experimental condition with no loss of data accuracy. These improvements allowed for a greater amount of data collection in a shorter period of time, while possibly reducing the effects of subject fatigue and vocal instability. [Research supported by NIH Grant No. DC02764.]

Nonlinear phenomena in the natural howling of a dog-wolf mix.

It was reported to the first author that a female dog-wolf mix showed anomalously rough-sounding vocalization. Spectral analysis of recordings of the vocalization revealed frequency occurrences of subharmonics, biphonation (two independent pitches) and chaos. Since these nonlinear phenomena are currently widely discussed as integral to mammalian vocalization [Wilden et al., Bioacoustics 9, 171-196 (1988)] or as indicators of vocal pathologies [Herzel et al., J. Speech Hearing Res. 37, 1008-1019 (1994); Riede et al., Z. Sgtkde 62 Suppl: 198-203 (1997)], we sought to understand the production mechanism of the observed vocal instabilities. First the frequency of nonlinear phenomena in the calls was determined for the female and four additional individuals. It turned out that these phenomena appear, but much less frequently in the repertoire of the four other animals. The larynges of the female and two other individuals were dissected post mortem. There was no apparent asymmetry of the vocal folds but a slight asymmetry of the arytenoid cartilages. The most pronounced difference, however, was an upward extension of both vocal folds of the female. This feature is reminiscent of "vocal lips" (syn. "vocal membranes") in some primates and bats. Spectral analysis of the female's voice showed clear similarities with an intensively studied voice of a human who produces biphonation intentionally. Finally, the possible communicative relevance of nonlinear phenomena is discussed.

Modelling biphonation — The role of the vocal tract

Instabilities of the human voice source appear in normal voices under certain conditions (newborn cries, vocal fry, creaky voice) and are symptomatic of voice pathologies. Vocal instabilities are intimately related to bifurcations of the underlying nonlinear dynamical system. We analyse in this paper bifurcations in 2-mass models of the vocal folds and study, in particular, how the incorporation of the vocal tract affects bifurcation diagrams. A comparison of a simplified model (Steinecke and Herzel, 1995) with an extended version including vocal tract resonances reveals that essential features of the bifurcation diagrams (as e.g. frequency locking of both folds and toroidal oscillations) are found in both model versions. However, vocal instabilities appear in the extended model at lower subglottal pressures and even for weak asymmetries.

Effects of botulinum toxin on vocal tract steadiness in patients with spasmodic dysphonia.

Since laryngeal botulinum toxin (BTX) injections have become the treatment of choice for spasmodic dysphonia, the purpose of this study was to examine its effects on the stability of the upper vocal tract as compared to the effects on glottic stability. Two different acoustic methods were used to analyze voice samples from 16 patients with adductor-type spasmodic dysphonias before and after BTX therapy and from a normal control group. Independent acoustic analyses were used to determine laryngeal and upper vocal tract stability. The results showed significantly higher values for the standard deviation of fundamental frequency (SDF0), reflecting laryngeal instability, for the patient group than for the control group and an impressive improvement for the patients after BTX therapy. Further, the equally high values of SDF0 for the initial second and a second from the midsegment of phonation were differentially reduced by BTX therapy, resulting in a normal pattern of laryngeal stability during sustained phonation. The variability of the first and second formants, reflecting upper vocal tract instability, showed higher values for the patients compared with the control group, but this difference was not statistically significant. The present findings showed that BTX injections to the thyroarytenoid muscle had no discernible effect on stability of the upper vocal tract.

Bifurcations in excised larynx experiments.

Bifurcation analysis was applied to vocal fold vibration in excised larynx experiments. Phonation onset and vocal instabilities were studied in a parameter plane spanned by subglottal pressure and asymmetry of either vocal fold adduction or elongation. Various phonatory regimes were observed, including single vocal fold oscillations. Selected spectra demonstrated correspondence between these regimes and vocal registers noted in the literature. To illustrate the regions spanned by the various phonatory regimes, two-dimensional bifurcation diagrams were generated. Many instabilities or bifurcations were noted in the regions of coexistence, i.e., regions in which the phonatory regimes overlap. Bifurcations were illustrated with spectrograms and fundamental frequency contours. Where possible, results from these studies were related to clinical observations.

Acoustic analysis of vocal instability in cerebellar dysfunctions.

Acoustic analysis of vocal instability during the production of isolated vowels, including computation of mean fundamental frequency (F0), period-to-period variability (jitter), pitch fluctuations, and between-trial variation of F0, was performed in 20 patients with cerebellar cortical dysfunction. Eleven subjects suffered from purely cerebellar atrophy (CA). In the remaining 9 patients olivopontocerebellar atrophy (OPCA) had been diagnosed. A subgroup of both the CA and OPCA subjects presented with enlarged pitch fluctuations and/or increased jitter values. It is conceivable that asymmetrically distributed motor deficits at the laryngeal level and altered gain settings of laryngeal and/or respiratory reflexes account for the observed phonatory instability. Moreover, 5 of the 20 cerebellar patients had a pitch level exceeding the upper limit of the normal range. Presumably, this deviation reflects increased vocal effort.

A model for neurologic sources of vocal instability

The activation and relaxation characteristis of thyroarytenoid and cricothyroid muscle twitches are used as basic building blocks to simulate a tetanic contraction in the laryngeal muscles. Approximately 100 motor units are used with random phase relationships and randomized firing rates. The fundamental frequency of the voice is calculated from the simulated tensions, and it is shown that jitter and shimmer vary inversely with mean motor unit firing rate and with the number of motor units within a given muscle. Jitter and shimmer vary directly with the coefficient of variation of motor unit size. Some low-frequency variations in F0 (tremor-like variation) are correlated with the mean firing rate of large single motor units. [Work supported by NINCDS Grant No. NS24409–02.]