Spectral analysis of sung vowels. III. Characteristics of singers and modes of singing.

The 1/3-oct spectra of nine different vowels, sung by 14 professional male and female singers in nine different modes of singing, were analyzed to reveal spectral characteristics of individual singers and modes of singing. The main spectral differences between singers could be described in two dimensions characterizing, respectively, differences among male and among female singers. Spectral characteristics of these dimensions suggested that interindividual differences among males, like the average difference between males and females, arise mainly from differences in vocal tract dimensions, whereas interindividual differences among females may have a glottal basis. The spectral characteristics of the modes of singing could be represented for each vowel in two dimensions. Differences among the soft (pianissimo), light, neutral, free, straight, extra vibrato, and loud (fortissimo) modes were mainly due to the spectral effect of vocal effort, which constituted a very dominant first spectral dimension. This dimension essentially reflected the slope of the spectrum. The second dimension mainly described the spectral differences between the dark and pressed modes of singing. A possible explanation of the results in terms of glottal and supraglottal morphological variation is discussed.