Laura Lehto

Systematic review of the treatment of functional dysphonia and prevention of voice disorders

OBJECTIVE To evaluate the effectiveness of interventions for treating functional dysphonia or preventing voice disorders in adults. DATA SOURCES We searched MEDLINE (1950 to 2006), EMBASE (1974 to 2006), CENTRAL (Issue 2 2006), CINAHL (1983 to 2006), PsychINFO (1967 to 2006), Science Citation Index (1986 to 2006), and the Occupational Health databases OSH-ROM (February 2006). REVIEW METHODS Systematic review and meta-analysis of randomized controlled trials. Included studies evaluated the effectiveness of interventions for 1) treating functional/nonorganic dysphonia or 2) preventing voice disorders. We identified six randomized controlled trials about treatment and two about prevention. Two authors independently extracted data and assessed trial quality. RESULTS A combination of direct and indirect voice therapy, compared with no intervention, improves self-reported (standardized mean difference -1.07; 95% CI -1.94 to -0.19), observer-rated (weighted mean difference [WMD] -13.00; 95% CI -17.92 to -8.08), and instrumentally assessed vocal functioning (WMD -1.20; 95% CI -2.37 to -0.03) in adults with functional dysphonia. Effects are reported to remain for at least 14 weeks. Effects are similar in patients and in teachers and student teachers screened for voice problems. We found two studies that did not show voice training, compared with no intervention, to have a preventive effective in improving self-reported vocal functioning. Assessment of publication bias showed that the real effect sizes are probably smaller. CONCLUSION Comprehensive voice therapy is effective in improving vocal performance in adults with functional dysphonia. There is no evidence of effectiveness of voice training in preventing voice disorders.

Occupational voice complaints and objective acoustic measurements-do they correlate?

To enable the development of appropriate diagnostics and treatment for occupational voice disorders, this study addresses connections between subjective voice complaints and objective observations. The subjects of this study were 24 female customer advisors, who mainly use the telephone during their working hours. During one working day, at four different times, speech samples covering 20 minutes of telephone conversation by the customer service advisors (CSAs) were recorded. In addition, the CSAs filled in a questionnaire (visual analogue scale) concerning their voice problems. To represent the vocal symptoms three variables were used: vocal fatigue, hoarseness and a general sum-variable. A 5-minute sample was taken from recordings for further analyses. This included fundamental frequency, sound pressure level, alpha ratio (the ratio between the spectral energy below and above 1000 Hz) and number of vocal fold vibrations. In the objective acoustic measurements, it was found that fundamental frequency (F0) rose significantly during the working day. Also the self-reported voice symptoms increased significantly during the working day. However, correlations between vocal symptoms and acoustic measures were not found.

Experiences of a Short Vocal Training Course for Call-Centre Customer Service Advisors

It is commonly known that occupational voice users suffer from voice symptoms to varying extents. The purpose of this study was to find out the effects of a short (2-day) vocal training course on professional speakers’ voice. The subjects were 38 female and 10 male customer advisors, who mainly use the telephone during their working hours at a call centre. The findings showed that although the subjects did not suffer from severe voice problems, they reported that the short vocal training course had an effect of some of the vocal symptoms they had experienced. More than 50% of the females and males reported a decrease in the feeling of mucus and the consequent need to clear the throat, and diminished worsening of their voice. Over 60% thought that voice training had improved their vocal habits and none reported a negative influence of the course on their voice. Females also reported a reduction of vocal fatigue. The subjects were further asked to respond to 23 statements on how they experienced the voice training in general. The statements ‘I learned things that I didn’t know about the use of voice in general’ and ‘I got useful and important knowledge concerning my work’ were highly assessed by both females and males. The results suggest that even a short vocal training course might affect positively the self-reported well-being of persons working in a vocally loading occupation. However, to find out the long-term effects of a short training course, a follow-up study would need to be carried out.

Voice symptoms of call-centre customer service advisers experienced during a work-day and effects of a short vocal training course

Occupational voice users often suffer from voice symptoms to varying extents. The first goal of this study was to find out how telephone customer service advisers experience voice symptoms at different moments of the working day. The second goal was to investigate the effects of a short vocal training course arranged for telephone workers. The results indicate that although the subjects did not suffer from severe voice problems, the short vocal training course significantly reduced some of the vocal symptoms they had experienced. The results suggest that systematic consultation and training for occupational voice users in the field of occupational voice care would be advantageous.

Objective quality measures for glottal inverse filtering of speech pressure signals

Glottal inverse filtering is a process where the effects of the vocal tract are cancelled from the speech signal in order to estimate the voice source. Traditionally, inverse filtering methods have involved a high level of manual tuning of parameters, such as the vocal tract model order. We present objective heuristics for the measurement of the quality of the resulting glottal flow estimate. In addition, we propose an automatic method for determining the order of the vocal tract all-pole model in inverse filtering based on phase-plane analysis and estimation of the glottal flow kurtosis.

Automatic pre-segmentation of running speech improves the robustness of several acoustic voice measures.

In order to study vocal loading, we developed a speech analysis environment for continuous speech. The objective was to build a robust system capable of handling large amounts of data while minimizing the amount of user-intervention required. The current version of the system can analyze up to five-minute recordings of speech at a time. Through a semiautomatic process it will classify a speech signal into segments of silence, voiced speech and unvoiced speech. Parameters extracted from the input signal include fundamental frequency, sound pressure level, alpha-ratio and speech segment information such as the ratio of speech to silence. This paper presents results from the performance evaluation of the system, which shows that the analysis environment is able to perform robust and consistent measurements of continuous speech.