Relationships of vowel characteristics to listener ratings of breathiness.

This experiment was designed to investigate the relationships of listener ratings of breathiness to vowel duration, speaking rate, and the relative energy in three frequency ranges (100-500, 1500-2500, and 3500-4500 Hz) in vowel spectra. The effects of vowel SPL also were considered. Listeners used a seven-point equal-appearing interval scale to rate a sentence spoken by each of 10 young adult females in each of four voice qualities: normal speech, mildly breathy, severely breathy, and whisper. Significant Pearson correlations to the ratings were found only for mean SPL and the relative energy in the 100-500 and 3500-4500 Hz ranges. After the effects of mean SPL were accounted for in partial correlation and multiple regression analyses, all vowel parameters were related significantly to the mean ratings. The partial correlations for vowel duration were as high as those for the three frequency ranges. Vowel duration may be as important as spectral characteristics of vowels when breathiness is judged from samples of connected discourse.