CLINICAL RELEVANCE OF THE FRACTAL DIMENSION OF F-0 PERTURBATIONS COMPUTED BY THE BOX-COUNTING METHOD

The box-counting method for determining the fractal dimension (D-fj) w as applied to the fundamental frequency (F-0) perturbations in normal and pathological voices in order to assess its clinical value. The upp er limit of these D-fj values was similar for both groups, but the dis tribution for pathological voices extended to lower values than for th e normal voices, However, these lower values were most probably the re sult of one or a few outlying frequency points due to incorrect determ ination of the vocal period. The D-fj of normal voices were within the range of values found for randomly varying F-0 values. It was conclud ed, that the vocal perturbations in pathological voices are also more or less randomly distributed. So, the D-fj, at that least determined w ith the box-counting method, do not contain clinically relevant-inform ation in addition to the traditional measures for the extent of the vo cal period perturbations. An exception is special perturbation types l ike diplophonia. The result of the computation is very sensitive for v oice breaks and vibrato and depends on the number of periods.