Perturbation measurements in highly irregular voice signals: Performances/validity of analysis software tools

In this paper we present results concerning validity of jitter measurement in strongly irregular voice signals (sustained vowels) moderately corrupted by noise. The performance of four tools for voice analysis is compared on synthetic signals as far as fundamental period and jitter estimation are concerned. Synthesised vowels offer the advantage of a perfect control of the amount of jitter put in. Though implementing the same formula for jitter estimation, the results obtained with these approaches become quite different for increasing jitter. The reason could be searched in the different methods used for the separation of voiced and unvoiced frames as well as for fundamental period estimation. Results show that all the tools give reliable results up to a jitter level J = 15%, that encompasses the ynthetic vowels maximum value J = 12% as obtained by expert raters by visual inspection. Hence, up to this limit, the tools presented here for jitter estimation can give a valid support to clinicians also in term of reproducibility of results and time saving. For jitter values larger than 15% all programs tend to underestimate the true jitter value, but with large differences among them. Just two methods succeed in estimating jitter values up to and larger than 20% and could thus be better suited for perturbation measure in strongly irregular voice signals.