Validation of Novel Clinical Scales for Perceptual Evaluation of Vocal Breathiness and Roughness

Perceived voice quality (VQ) ratings provide data with ordinal characteristics on arbitrary scales regarding the relative order of VQ disruptions ranging from mild to severe quality. The overarching goal of this research is to develop a new and rigorous method for perceptual evaluation of VQ using quantitative comparisons and facilitating standardized comparisons across time points, clinicians, and clinical sites. Our prior research developed standard ratio-level scales of breathy and rough VQ analogous to the sone scale that (a) have physical units, (b) are strongly related to psychophysical measures, and (c) can quantify not just the direction but also the magnitude of change. The current study reestablishes the standard reference points, validates the newly developed VQ scales with natural dysphonic stimuli, and evaluates the psychometric measurement properties of the novel scales for breathiness and roughness in a small clinical pilot experiment.

In the first experiment, a set of magnitude estimation (ME) tasks were first used to determine the perceived magnitudes of breathiness and roughness of 10 natural voice stimuli in each VQ continuum. The resulting data were compared with previously acquired magnitude estimates of the synthetic comparison stimuli to adjust the reference points. In the second experiment, a set of inexperienced listeners evaluated the same set of natural dysphonic stimuli using the new clinical scales with perceived magnitude expressed in standard VQ units. In the third experiment, two expert clinicians evaluated 12 breathy and 10 rough dysphonic voices (pre- and posttreatment) using the new VQ scales.

The standard reference units were identified as 15 dB SNR for breathiness and -26 dB modulation depth for roughness. The strength of the relationship between the ME data and the predicted values from the clinical scales was high for both breathiness and roughness (r > .9). Treatment outcomes measured using the newly developed scales demonstrated high intra- (r > .8) and interrater reliability (r > .8) when compared to Consensus Auditory-Perceptual Evaluation of Voice providing evidence for concurrent validity of the clinical scales.

Such formal VQ scales support valid quantitative comparisons of perceptual judgments and represent a critical step in clinical translation.