Validation of the Acoustic Voice Quality Index Version 03.01 and Acoustic Breathiness Index in German

Objective. The aim of this study was to validate the acoustic voice quality index (AVQI) version 03.01 and the acoustic breathiness index (ABI) in the German language. Methods. Concatenated voice samples of continuous speech (cs) and sustained vowel (sv) [a:] from 175 subjects with dysphonia and 43 vocally healthy subjects were perceptually judged for overall voice quality and breathiness severity. First, to reach a higher level of ecological validity, the proportions of cs and sv were equalized regarding the time length. Second, concurrent validity and diagnostic accuracy were statistically verified using the Spearman rank-order correlation coefficient (r(s)) and several estimates of the receiver operating characteristics, likelihood ratio, and Youden index. Results. A moderate reliability of overall voice quality and breathiness severity from three experts were found. It was found that 27 syllables as standardization of the cs part, which represents 3 seconds of voiced cs, allows the equalization of both speech tasks. A strong correlation was revealed between AVQI and overall voice quality (r(s) = 0.86, P < 0.01), and ABI and perceived breathiness severity (r(s) = 0.85, P < 0.01). Additionally, the best diagnostic outcome for AVQI and ABI was identified at a threshold of 1.85 (sensitivity of 72 % and specificity of 90 %) and 3.42 (sensitivity of 72 % and specificity of 95 %), respectively. Conclusion. AVQI and ABI showed in the German language valid and robust results to quantify abnormal voice qualities regarding overall voice quality and breathiness severity.