Correlation of instrumental voice evaluation with perceptual voice analysis using a modified visual analog scale

Various rating scales have been used for perceptual voice analysis including ordinal (ORD) scales and visual analog (VA) scales. The purpose of this study was to determine the most suitable scale for studies using perceptual voice analysis as a gold standard for validation of objective analysis protocols. The study was carried out on 74 female voice samples from 68 dysphonic patients and 6 controls. A panel of 4 raters with experience in perceptual analysis was asked to score voices according to the G component (overall quality) of the GRBAS system. Two rating scales were used. The first was a conventional 4-point ORD scale. The second was a modified VA (mVA) scale obtained by transforming the VA scale into an ORD scale using a weighted conversion scheme. Objective voice evaluation was performed using the EVA workstation. Objective measurements included acoustic, aerodynamic, and physiologic parameters as well as parameters based on nonlinear mathematics (e.g., Lyapunov coefficient). Instrumental measurements were compared with results of perceptual analysis using either the conventional ORD scale or mVA scale. Results demonstrate that correlation between perceptual and objective voice judgments is better using a mVA scale than a conventional ORD scale (concordance, 88 vs. 64%). Data also indicate that the mVA scale described herein improves the correlation between objective and perceptual voice analysis.