Comparison of acoustic voice perturbation measures among three independent voice laboratories

The purpose of this study was to compare jitter and shimmer data measured with three different analysis systems, the Visi-Pitch PC system (Pine Brook) and two systems based on minicomputers (Chicago and Denver), as a preliminary step toward establishing recording and analysis standards. The results show that, although similar hardware and software used at independent laboratories can yield similar findings, differences in recording hardware as well as recording and analysis procedures can result in important differences in perturbation findings. Jitter measurements obtained with the Visi-Pitch were not consistently in good agreement with jitter measurements obtained from the minicomputer systems due, in part, to an interaction between the Visi-Pitch internal filter selected during the recording process and the novel method of pitch period determination used in the Visi-Pitch. Magnitude of shimmer measurements differed between the two minicomputer systems, in part because of differences in amplitude resolution of the A/D converters and recording noise. The correlation between the two shimmer data sets was relatively high, however, indicating that relative changes across utterances were comparable in spite of magnitude differences.