The Perception of Formant Tuning in Soprano Voices

Abstract 0.1. Introduction At the upper end of the soprano singing range, it is known that singers alter the shape of their vocal tracts in order to bring one or more of the vocal tract resonances nearer to a harmonic of the voice source; a process known as resonance tuning, which increases the amplitude of the sound produced with little eort from the singer. This study investigated the perception of first and second resonance tuning; key strategies observed in classically trained soprano voices. It was expected that the most commonlyused strategies observed in singers would be preferred by the listeners, and since previous investigations have often focussed only on a single vowel sound (usually /A/), this test will also allow for comparison of dierent tuning strategies between vowels. 0.2. Method Synthetic vowel sounds were generated using an L-F glottal flow model, passed through a series of filters to represent the vocal tract resonances. Listeners then compared the sounds, which included 3 vowels, at 4 fundamental frequencies ( f0), to which 4 dierent tuning strategies were applied; (A) the expected formant values in speech, (B) the first formant tuned to the fundamental, (C) the second formant tuned to the second harmonic, and (D) both first and second formants tuned to the first and second harmonics respectively. Participants were asked three sets of questions: comparing how much they preferred dierent tuning strategies, how natural they found dierent tuning strategies, and identifying the vowel of each sound. 0.3. Results The results obtained varied greatly between vowels; the results for the /A/ vowel were similar for preference and naturalness, but no clear pattern was seen for vowel identification. The results for the /u/ vowel did not appear to show a clear dierence between the dierent tuning strategies for preference, and only a little separation for naturalness. The vowel identification was generally very poor for this vowel. The results for the /i/ vowel were striking, with strategies including R2 tuning both preferred and perceived as more natural than those without for both preference and naturalness, however for the vowel identification, strategies without R2 tuning were most often correctly identified. 0.4. Conclusion The results indicate that the perception of dierent tuning strategies alters depending on the vowel and the perceptual quality investigated (preference, naturalness, or vowel identification), and whether the first and second harmonic fall above or below the first or second formants. For some vowels and perceptual qualities, formant tuning was found to be beneficial at lower f0 values than expected based on current expectations of formant tuning in practice.