Successful communication depends partly on the optimal use of voice. A large portion of the South African population depends on this optimal use of voice for their occupations. Voice problems for the professional voice user in particular therefore impact negatively on their livelihood. It is, however, especially professional voice users who are at risk of developing functional voice problems. One such a population is teachers. Teachers frequently experience voice problems due to functional voice hyperfunction (the excessive and incorrect use of voice). The South African school milieu with its high learner to teacher ratio, as well as the multilingual and multicultural nature of the learners, contribute to this vocal hyperfunction because of a higher level of background noise and the need to repeat instructions. Furthermore, it appears that these occupational responsibilities often complicate the successful implementation of the usual vocal exercise maintenance strategies.
The main objective of this single-case study was to investigate the application value of personal amplification as an augmentative option for teachers with occupationally related voice problems. Subsidiary aims were to determine specific aspects before and after the usual vocal exercise maintenance strategies. In addition to these, aspects pertaining to the effect of the usual maintenance in combination with personal sound amplification were investigated. The subsidiary aims were therefore to compare and analyse these strategies perceptually and acoustically.
Specific perceptual and acoustic voice characteristics of a teacher were evaluated. These evaluations took place before and after a period during which a voice amplification device was used as a supportive strategy to the usual maintenance strategies. Qualitative and quantitative comparison of the data took place by comparing the results of the various evaluations in phases 1 and 2.
During this study, the participant displayed a persistent nodule of the vocal cord, which had to be surgically removed in the best interest of the participant. This ad hoc adaptation to the research design was necessary although not initially planned. The research design was accordingly adapted, and the investigation therefore included a pre- and post-surgical phase. Ethical clearance had been obtained for both phases.
Perceptual evaluations: Average scale evaluations of the individual participants of the listeners’ panel (there were six listeners) were calculated to determine the final listener panel score. These evaluations were done using a rater’s scale form on which the listener panel evaluated the spontaneous answers to questions and a paragraph of reading according to eight combined speech stimuli. Listeners had to rate the extent to which voice quality deviated or not. During evaluations 1–3 the six listeners concurred in general that the participant’s use of voice, sounded moderately impaired. The surgical intervention improved the participant’s use of voice, according to the perceptual evaluation. The evaluation that was completed after the two maintenance strategies were implemented indicated a further normalisation of the voice quality of the participant. During the second phase no obvious difference between the effects of the various maintenance strategies was noted. The most obvious difference was the improvement in auditory perceptual voice quality after surgical intervention.
Acoustic analyses: Various parameters related to voice quality were measured with the Multi Dimensional Voice Programme (MDVP) and compared. The average of the three measurements during each evaluation was calculated for each of the parameters. The results of the first and second reversed phase were compared to serve as a control. During evaluation 1–5 the fundamental frequency (F0) was within the norm for female speakers of the age group of the participant. However, this parameter increased slightly during evaluation 6–8. The F0 is related to the mass of the vocal cords. A lower mass results in an increase in the F0. The removal of vocal cord nodules (such as before evaluation 6) and the resultant reduction of mass will lead to a higher F0. This increased F0 was evidenced by the results of the second phase.
The perceptual and acoustic analysis of voice quality corroborated the positive effect of the surgical intervention. Although the listeners’ panel did not notice the improvement in the participant’s voice quality, various acoustic voice parameters improved after the use of the personal voice amplification as an additional maintenance strategy. The conclusion was made that personal voice amplification as an augmentative strategy to usual vocal exercise maintenance strategies could be of value to teachers who experience occupation-related voice problems. The combined strategy had a positive influence on most of the acoustic parameters, although the listeners did not note the same level of difference.
This study has added value to evidence-based practice in the field of voice therapy. Similar studies in which participants with organic voice pathologies (such as vocal cord nodules) are compared with studies of participants with healthy vocal cords may also shed more light on the mechanism of functional voice hyperfunction (Boone, McFarlane, Von Berg and Zraick 2009). The use of physiological methods of analyses could, for example, be used to trace the subtle changes in voice. The results of the present study confirmed that there is a definite need for further research to highlight the role of a single listener or a panel of listeners in detecting voice pathologies. Acoustic parameters and terminology describing the perceptually/auditorily detectable correlates also have to be studied in depth. Furthermore, the value of voice amplification for patients with Parkinson’s disease, for example, could be explored as well. Results of the present study may serve as a starting point to motivate funding of such amplification apparatus by the medical aid companies. The availability of these apparatuses in South Africa specifically must be considered due to high importing costs. Linking with local electronic engineers for the design of similar, but more cost-effective amplification apparatus than the model used in the present research may also provide work and study opportunities within the South African context.
Keywords: acoustic voice properties; functional voice hyperfunction; functional voice problems; perceptual voice properties; professional voice users; teachers; voice amplification; voice maintenance; voice problems
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