Acoustic and perceptual assessment of vibrato quality of singing students

While most studies that attempted to evaluate vibrato quality examined vocal productions of accomplished singers, very little is known about the characteristics of vibrato among singing students. Therefore, in this study, we performed a preliminary attempt to assess vibrato quality in their production of sustained notes. To that end, the presence and quality of vibrato in 253 sung notes was rated subjectively by five experienced singing teachers. The pitch contour was calculated for each recording, from which we calculated the FFT and the autocorrelation of this contour. Subsequently, a series of features was extracted from these two, and then different statistical methods were applied to examine whether the acoustic features could be used to define predictors that would be in agreement with the perceptual judgments. Given the moderate agreement obtained among judges, these acoustic predictors performed relatively well: vibrato existence was predicted correctly in over 82% of the recordings. The predictor for vibrato quality accounted for 46.5% of the variance of the subjective evaluation of vibrato quality. Due to the novelty of this study in assessing vibrato among students rather than among professional singers, several considerations and limitations, as well as directions for further research are discussed.