What makes a voice outstanding: vibrato and power of sound are important

A new study from Japan has for the first time attempted to provide a scientific answer to this question, revealing the hidden mechanisms behind the evaluation of opera singing.

A team of researchers from Keio University, led by Haruka Kondo, a PhD student and part-time soprano opera singer, conducted an in-depth statistical analysis to find out which vocal and acoustic parameters determine the final score in competitions. As it turned out, two parameters are most important: vibrato and voice power ratio (SPR), which is related to the so-called "singer's formant" - the ability of the voice to fill the room without a microphone.

Ten professionally trained Japanese opera singers participated in the experiment, each singing the classical Italian aria "Caro mio ben". Their recordings were evaluated by four experienced vocal pedagogues, who gave both an overall score and a score on six criteria: vibrato, resonance, timbre, diction, intonation and expressiveness. At the same time, the scientists measured the acoustic parameters of the recording: SPR, HNR (harmonic to noise ratio, which determines the purity of the sound) and LUFS (loudness level).

The analysis showed that vibrato is the most important vocal parameter, while the others (e.g. timbre and diction) do not have a statistically significant impact on the final score. Of the acoustic characteristics, SPR was decisive, while HNR and LUFS had almost no influence on the result. The scientists explain this by the fact that professional vocalists have inherently high voice quality and low noise levels, and that loudness alone does not determine artistic perception.

"Our study provides insight into exactly how judges form their opinions," says Professor Shinya Fujii. - 'This opens up new possibilities for objective vocal pedagogy and helps singers to develop key parameters in a targeted way'."

Dr Sotaro Kondo adds: "We are approaching a time when it will be possible to not only rely on the teacher's judgement in a vocal lesson, but also to monitor the parameters of one's voice in real time on a screen."

The work of Kondo and Fujii's team thus makes an important contribution to understanding the relationship between art and science. In the future, this data may help not only young singers on the road to professionalism, but also educators seeking accurate and scientifically sound vocal training methods.