[Functional disorders of the voice and their treatment (author's transl)]

'Malregulative' Rather Than 'Functional' Dysphonia: A New Etiological Terminology Framework for Phonation Disorders-A Position Paper by the Union of European Phoniatricians (UEP)

Practitioners in the field of voice are often faced with patients who are 'dysphonic', but who do not have identifiable abnormalities of the vocal tract structures or any neural or hormonal alteration affecting the phonatory function. For lack of better nomenclature describing the origin of the disorder, this group of patients has been labeled as having 'non-organic' or 'functional' dysphonia. 'Non-organic' only states what the dysphonia is not, and 'functional' does not have any etiological implication. Hence 'functional disorder' as a determination of the origin is at best vague, imprecise and often misleading. In truth, the terms "functional" and 'non-organic' are by now so muddled and confused in everyday clinical usage and parlance that it is unclear what they mean in any given clinical setting or for any particular clinical case. Thus, the UEP Voice Committee (VC) has come to the conclusion that it is best to adopt a new term that is clearly defined, universally agreed to, and indicative of a different and more useful perspective. We have reviewed the literature relating to terminology of these phonatory disorders. We now propose replacement of the phrase 'functional dysphonia' with 'malregulative dysphonia', since the indication of faulty regulation represents an etiological connotation. We also propose a restructuring of the etiological terminology of phonation disorders. We believe this to be a biologically clearer framework for the labeling of 'non-organic' phonatory disorders, and hope that its routine use will allow for more clarity of presentation and discussion in the future.

A Randomized Controlled Trial of Two Semi-Occluded Vocal Tract Voice Therapy Protocols

PURPOSE

Although there is a long history of use of semi-occluded vocal tract gestures in voice therapy, including phonation through thin tubes or straws, the efficacy of phonation through tubes has not been established. This study compares results from a therapy program on the basis of phonation through a flow-resistant tube (FRT) with Vocal Function Exercises (VFE), an established set of exercises that utilize oral semi-occlusions.

METHOD

Twenty subjects (16 women, 4 men) with dysphonia and/or vocal fatigue were randomly assigned to 1 of 4 treatment conditions: (a) immediate FRT therapy, (b) immediate VFE therapy, (c) delayed FRT therapy, or (d) delayed VFE therapy. Subjects receiving delayed therapy served as a no-treatment control group.

RESULTS

Voice Handicap Index (Jacobson et al., 1997) scores showed significant improvement for both treatment groups relative to the no-treatment group. Comparison of the effect sizes suggests FRT therapy is noninferior to VFE in terms of reduction in Voice Handicap Index scores. Significant reductions in Roughness on the Consensus Auditory-Perceptual Evaluation of Voice (Kempster, Gerratt, Verdolini Abbott, Barkmeier-Kraemer, & Hillman, 2009) were found for the FRT subjects, with no other significant voice quality findings.

CONCLUSIONS

VFE and FRT therapy may improve voice quality of life in some individuals with dysphonia. FRT therapy was noninferior to VFE in improving voice quality of life in this study.

Artificially lengthened and constricted vocal tract in vocal training methods

It is common practice in vocal training to make use of vocal exercise techniques that involve partial occlusion of the vocal tract. Various techniques are used; some of them form an occlusion within the front part of the oral cavity or at the lips. Another vocal exercise technique involves lengthening the vocal tract; for example, the method of phonation into small tubes. This essay presents some studies made on the effects of various vocal training methods that involve an artificially lengthened and constricted vocal tract. The influence of sufficient acoustic impedance on vocal fold vibration and economical voice production is presented.

Effects of a semioccluded vocal tract on laryngeal muscle activity and glottal adduction in a single female subject

Voice training exploits semiocclusives, which increase vocal tract interaction with the source. Modeling results suggest that vocal economy (maximum flow declination rate divided by maximum area declination rate, MADR) is improved by matching the glottal and vocal tract impedances. Changes in MADR may be correlated with thyroarytenoid (TA) muscle activity. Here the effects of impedance matching are studied for laryngeal muscle activity and glottal resistance. One female repeated [pa:p:a] before and immediately after (a) phonation into different-sized tubes and (b) voiced bilabial fricative [beta:]. To allow estimation of subglottic pressure from the oral pressure, [p] was inserted also in the repetitions of the semiocclusions. Airflow was registered using a flow mask. EMG was registered from TA, cricothyroid (CT) and lateral cricoarytenoid (LCA) muscles. Phonation was simulated using a 7 x 5 x 5 point-mass model of the vocal folds, allowing inputs of simulated laryngeal muscle activation. The variables were TA, CT and LCA activities. Increased vocal tract impedance caused the subject to raise TA activity compared to CT and LCA activities. Computer simulation showed that higher glottal economy and efficiency (oral radiated power divided by aerodynamic power) were obtained with a higher TA/CT ratio when LCA activity was tuned for ideal adduction.

Voice training and therapy with a semi-occluded vocal tract: rationale and scientific underpinnings

PURPOSE

Voice therapy with a semi-occluded vocal tract has a long history. The use of lip trills, tongue trills, bilabial fricatives, humming, and phonation into tubes or straws has been hailed by clinicians, singing teachers, and voice coaches as efficacious for training and rehabilitation. Little has been done, however, to provide the scientific underpinnings. The purpose of the study was to investigate the underlying physical principles behind the training and therapy approaches that use semi-occluded vocal tract shapes.

METHOD

Computer simulation, with a self-oscillating vocal fold model and a 44 section vocal tract, was used to elucidate source-filter interactions for lip and epilarynx tube semi-occlusions.

RESULTS

A semi-occlusion in the front of the vocal tract (at the lips) heightens source-tract interaction by raising the mean supraglottal and intraglottal pressures. Impedance matching by vocal fold adduction and epilarynx tube narrowing can then make the voice more efficient and more economic (in terms of tissue collision).

CONCLUSION

The efficacious effects of a lip semi-occlusion can also be realized for nonoccluded vocal tracts by a combination of vocal fold adduction and epilarynx tube adjustments. It is reasoned that therapy approaches are designed to match the glottal impedance to the input impedance of the vocal tract.

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

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 (hypertonic 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.

Effects of amplified and damped auditory feedback on vocal characteristics

This study tested two possible methods for reducing vocal load e.g. during classroom speech. Six female subjects read aloud from a text (1) under normal circumstances, (2) while hearing their own voice amplified (through headphones) and (3) with auditory feedback damped by foam plastic earplugs inserted in the outer ear canal. Fundamental frequency (F0) and sound pressure level (SPL) decreased during both amplified and damped feedback. Additionally, during amplification the relative level of F0 compared to that of the first formant diminished, likewise the alpha ratio. These changes may indicate reduced vocal fold adduction. The results suggest that both amplification and damping of auditory feedback may reduce vocal load during phonation.

Acoustic impedance of an artificially lengthened and constricted vocal tract

Voice training techniques often make use of exercises involving partial occlusion of the vocal tract, typically at the anterior part of the oral cavity or at the lips. In this study two techniques are investigated: a bilabial fricative and a small diameter hard-walled tube placed between the lips. Because the input acoustic impedance of the vocal tract is known to affect both the shaping of the glottal flow pulse and the vibrational pattern of the vocal folds, a study of the input impedance is an essential step in understanding the benefits of these two techniques. The input acoustic impedance of the vocal tract was investigated theoretically for cases of a vowel, bilabial occlusion (fully closed lips), a bilabial fricative, and artificially lengthening the tract with small diameter tubes. The results indicate that the tubes increase the input impedance in the range of the fundamental frequency of phonation by lowering the first formant frequency to nearly that of the bilabial occlusion (the lower bound on the first formant) while still allowing a continuous airflow. The bilabial fricative also has the effect of lowering the first formant frequency and increasing the low-frequency impedance, but not as effectively as the extension tubes.