Normalization patterns of the surface electromyographic signal in the phonation evaluation

Towards Evaluating Pitch-Related Phonation Function in Speech Communication Using High-Density Surface Electromyography

Pitch, as a sensation of the sound frequency, is a crucial attribute toward constructing a natural voice for communication. Producing intelligible sounds with normal pitches depend on substantive interdependencies among facial and neck muscles. Clarifying the interrelations between the pitches and the corresponding muscular activities would be helpful for evaluating the pitch-related phonating functions, which would play a significant role both in training pronunciation and in assessing dysphonia. In this study, the speech signals and the high-density surface electromyography (HD sEMG) signals were synchronously acquired when phonating [a:], [i:], and [ә:] vowels with increasing pitches, respectively. The HD sEMG energy maps were constructed based on the root mean square values to visualize spatiotemporal characteristics of facial and neck muscle activities. Normalized median frequency (nMF) and root-mean square (nRMS) were correspondingly extracted from the speech and sEMG recordings to quantitatively investigate the correlations between sound frequencies and myoelectric characteristics. The results showed that the frame-wise energy maps built from sEMG recordings presented that the muscle contraction strength increased monotonously across pitch-rising, with left-right symmetrical distribution for the face/neck. Furthermore, the nRMS increased at a similar rate to the nMF when there were rising pitches, and the two parameters had a significant correlation across different vowel tasks [(a:) (0.88 ± 0.04), (i:) (0.89 ± 0.04), and (ә:) (0.87 ± 0.05)]. These findings suggested the possibility of utilizing muscle contraction patterns as a reference for evaluating pitch-related phonation functions. The proposed method could open a new window for developing a clinical approach for assessing the muscular functions of dysphonia.

Effects of Voiced Gargling on the Electrical Activity of Extrinsic Laryngeal Muscles and Vocal Self-assessment

OBJECTIVE

To verify the immediate effects of voiced gargling on the electrical activity of extrinsic laryngeal muscles and vocal self-assessment.

METHODS

A sample of 20 individuals of both sexes, mean age of 31.95 (±11.57) years, were equally divided in two groups according to the presence or absence of vocal complaint. Both groups were evaluated by surface electromyography of the suprahyoid (SH) and infrahyoid (IH) muscle areas during rest, phonation of the sustained vowel [Ɛ] in habitual and strong intensities; phonation of rising and falling glissando; and counting from 1 to 10. Surface electromyography was assessed before and after the voiced gargling exercise, which lasted 1 minute. All participants self-rated their voice and phonatory comfort after the exercise. Wilcoxon and Mann-Whitney tests were applied, as well as Fisher's exact test and linear-to-linear test. The level of significance was 5%.

RESULTS

The percentage of electrical activity of the SH muscle area decreased in the glissando and counting tasks in the group with vocal complaint, as well as in phonation of sustained vowel in strong intensity in the group without complaint. Decrease was also observed in the right IH muscle area at rest and during sustained vowel phonation at habitual and strong intensities. Percentage of muscular electrical activity was lower in the group with complaint in the following situations: IH muscle area on both sides, at rest and during habitual phonation of sustained vowel and glissando before and after the exercise; right IH muscle area, during counting and strong phonation of sustained vowel before and after exercise; left IH muscle area, in the counting task, just after intervention. Most participants noticed improvement in voice (70%) and phonatory comfort (65%).

CONCLUSIONS

Voiced gargling during 1 minute promotes immediate effects on the electrical activity of the extrinsic laryngeal muscles in individuals with or without vocal complaint. Most individuals reported improved voice and phonatory comfort after exercise.

Effects of transcutaneous electrical nervous stimulation (TENS) associated with vocal therapy on musculoskeletal pain of women with behavioral dysphonia: A randomized, placebo-controlled double-blind clinical trial

Recently, electrical stimulation in vocal rehabilitation has been the subject of studies. This treatment has shown promising results regarding the decrease of vocal/laryngeal symptoms, pain and the improvement of vocal tension. In addition to decreasing pain symptoms, TENS treatments may lead to muscle relaxation. There is no data on the effects of this resource as a vocal therapy in women with behavioral dysphonia. Research in this area may provide evidence to assist the clinical decision related to the treatment of women with complaints of behavioral dysphonia and musculoskeletal pain.

OBJECTIVE

To verify the effects of low-frequency TENS in association with vocal therapy on musculoskeletal pain in women with behavioral dysphonia.

METHODS

Participants included 27 women with vocal nodules randomized into two groups. The experimental group (EG) - 13 women received 12 sessions of TENS (pulse of 200 μs, frequency at 10 Hz, in motor threshold) with electrodes placed bilaterally on the trapezius muscle and submandibular area for 20 min followed by 30 min of vocal therapy, and the control group (CG) - 14 women received 12 sessions of 20 min of a placebo TENS followed by 30 min of vocal therapy. We investigated the frequency and intensity of the musculoskeletal pain in several body regions, as well as the intensity of pain at rest and in the application of pressure with an algometer applied to the descending fibers of the trapezius muscle. The pressure-pain threshold (PPT) was also investigated. All evaluations occurred before, immediately after, and at one and three months after treatment in both groups.

RESULTS

We observed a reduction in the frequency of pain in the larynx after treatment of both groups, but only the EG showed a decrease in pain intensity in this region. It was verified with an algometer to the trapezius muscle that the electrical stimulation associated with the vocal therapy decreased the intensity of pain during the application of pressure and increased the PPT. There were no significant differences with regard to variables investigated in the comparison between the interventions. On the other hand, there was decreased pain in the trapezius muscle for the EG in comparison to the pre- and post-intervention.

CONCLUSION

The vocal therapyprogram reduced the frequency and intensity of the musculoskeletal pain in the regions proximal to the larynx of women with behavioral dysphonia. In addition, TENS followed by vocal therapy increased the threshold of sensitivity to muscular pain in the trapezius, demonstrating that it is a good resource to use in conjunction with traditional vocal therapy in cases of behavioral dysphonia associated with pain and muscle tension.

High-density surface electromyography: A visualization method of laryngeal muscle activity

OBJECTIVES/HYPOTHESIS

Laryngeal muscle activation is a complex and dynamic process. Current evaluation methods include needle and surface electromyography (sEMG). Limitations of needle electromyography include patient discomfort, interpretive complexity, and limited duration of recording. sEMG demonstrates interpretive challenges given loss of spatial selectivity. Application of high-density sEMG (HD sEMG) arrays were evaluated for potential to compensate for spatial selectivity loss while retaining benefits of noninvasive monitoring.

STUDY DESIGN

Basic science.

METHODS

Ten adults performed phonatory tasks while a 20-channel array recorded spatiotemporal data of the anterior neck. Data were processed to provide average spectral power of each electrode. Comparison was made between rest, low-, and high-pitch phonation. Two-dimensional (2D) spectral energy maps were created to evaluate use in gross identification of muscle location.

RESULTS

Three phonatory tasks yielded spectral power measures across the HD sEMG array. Each electrode within the array demonstrated unique power values across all subjects (P < .001). Comparison of each electrode to itself across phonatory tasks yielded differences in all subjects during rest versus low versus high, rest versus low, and rest versus high and in 9/10 subjects (P < .001) for low versus high phonation. Symmetry of HD sEMG signal was noted. Review of 2D coronal energy maps allowed for gross identification of cricothyroid muscle amidst anterior strap musculature.

CONCLUSIONS

HD sEMG can be used to identify differences in anterior neck muscle activity between rest, low-, and high-pitch phonation. HD sEMG of the anterior neck holds potential to enhance diagnostic and therapeutic monitoring for pathologies of laryngeal function.

LEVEL OF EVIDENCE

NA Laryngoscope, 129:2347-2353, 2019.

A pilot study on the evaluation of normal phonating function based on high-density sEMG topographic maps

Phonation is controlled by complex synergism of muscles over the front neck region. Proper evaluation of the muscular activities in this region would not only help to estimate phonation function, but may also provide characteristics to diagnose dysphonia. While surface electromyography (sEMG) technique has been used to study the physiological aspects of phonation in previous studies, it remains unclear if the phonating function could be dynamically characterized by the sEMG signals of the neck muscles associated with phonation. In this study, almost 80 channels of high-density (HD) sEMG signals were acquired from four healthy subjects when the vowel /a/ was phonated across different pitches by them. The root mean square (RMS) of the HD sEMG signals was computed within a series of segmented analysis windows and used to construct dynamic sEMG topographic maps. And the RMS maps represented the energy distribution of the front neck muscles, which would provide both the temporal and spatial information in accordance with the physiological and biomechanical principles of phonation. Our pilot results from the sEMG topographic maps across different pitch levels showed that the muscular activities consistently increased with the enhancement of the pitch levels. This pilot study suggests that HD sEMG might be a potential tool to visualize the distribution of the muscular activities and observe the coordination of muscular contractions during phonation. Also, it might pave way for proper screening and diagnosis of dysphonia as well as its associated pathologies.