Lyric or Dramatic - Vibrato Analysis for Voice Type Classification in Professional Opera Singers
Vibrato is one of the most frequently investigated parameters in singing. Most studies examine a very limited number of sound samples to answer specific questions. In the novel approach of our interdisciplinary vibrato project, a sophisticated database of 1723 sound samples was compiled, containing examples from 30 operas, one oratorio and 73 vocal exercises. Single tones undisturbed by orchestral sound were selected in the vocal registers soprano, tenor, baritone and bass according to a standardized classification system dividing voices into either a lyric or dramatic voice type. Various algorithms were implemented in a Matlab environment to automatically evaluate sound samples, with respect to vibrato extent and rate. An AM/FM demodulation scheme is presented with postprocessing required for automatic calculation of these two parameters. The vibrato extent was higher for the dramatic compared to the lyric voice type in soprano and tenor voices. In contrast, the extent of lyric baritones was significantly higher than for dramatic ones. Moreover, the vibrato rate was slightly lower for the dramatic voice type in all vocal registers. It turned out that the classification of bass voices into lyric and dramatic, unlike the other vocal registers, was not scientifically reproducible with our methods. Further vibrato results regarding aging, intra-individual and general stylistic development over time are presented and their essential relevance for vocal pedagogy are discussed.