[Objective evaluation of dysphonia. Possibilities and limitations]

Today clinical evaluation of the presence and extent of dysphonia is still essentially based on subjective-perceptive criteria. The lack of objectivity and the one-sidedness of such an approach reinforces the desire for a quantitative, objective determination of dysphonia which could aid in making an modern, unequivocal evaluation of the presence, extent and variations in time of this disorder both upon onset and after treatment. The purpose of the present research was to determine the reliability, possibilities and limitations of an objective, parametric procedure to evaluate both the normal and pathological voice. This procedure is based on the detection of the relationship between the noise and harmonic portions in the voice (the Yumoto H/N ratio). The study involved a group of 208 subjects (148 with dysphonia and 60 normal) and the procedure was applied using computerized digital sonography and dedicated algorithms. The results of this research showed that the vocal analysis procedure developed by Yumoto is not only simple but also highly sensitive, providing an objective study of dysphonia. In fact, the comparison between the average H/N ratio recorded in our patients (1.697 dB) is significantly different from that recorded in the normal subjects (11.169 dB) (p < 0.001). This also showed a clear discrimination between the two groups with no borderline or overlapping data found. The initial evaluation does not appear to establish a relationship between abnormal H/N ratio values and the type of pathology although greater morphological destruction of the vocal cords corresponds to worse vocal quality and therefore increased noise. For the data obtained to be valid, a necessary condition is the application of a strict, precise, correct sampling and analysis method following well-defined rules. Finally, the values obtained can serve as a basis for the construction of an objective instrumental voice measurement protocol that can be used in forensic evaluation of dysphonia. Standardization of the regulations is essential to such a project.