The Dynamic Effect of the Valleculae on Singing Voice - An Exploratory Study Using 3D Printed Vocal Tracts.

Background And Objectives: The valleculae can be seen as a pair of side branches of the human vocal tract like the piriform fossae. While the acoustic properties of the piriform fossae have been explored in detail, there is little evidence of full exploration of the acoustic properties of the valleculae. A recent investigation (Vampola, Horáček, & Švec, 2015), using a finite element model of a single vowel /a/, suggests that the valleculae created two antiresonances and two resonances in the high frequency region (above 4kHz) along with those produced by the piriform sinuses. In the current study, we investigate, in multiple vowels, the acoustic influences of the valleculae in singing voice, using 3-D printed vocal tracts.

Method: MRI data were collected from an operatic tenor singing English vowels /a/, /u/, /i/. The images of each vowel were segmented and edited to create a pair of tracts, where one is the original and one had the valleculae digitally removed.The printed tracts were then placed atop a vocal tract organ loudspeaker, excited by white noise. Recordings were made with a microphone placed in front of the mouths of the tracts, to measure their frequency responses.

Results: Dimensional changes were observed in valleculae of different vowels, with the long-term average spectra of the recordings illustrating clear differences between the frequency responses of the va-nova (valleculae - no valleculae) pairs, which varies with vowels.

Conclusion: The experiment demonstrates the dynamic nature of the shapes of the valleculae in the human vocal tract and its acoustic consequences. It provides evidence that the valleculae have similar acoustic properties to the piriform fossae but with larger variations, and in some cases can influence acoustically the frequency region below 4kHz. The results suggest that large volume valleculae have the potential to impede to some extent the acoustic effect of the singers formant cluster and small valleculae may do the reverse. Since the volume of the valleculae is observed to be largely dependent on tongue movement and also with changes to the uttered vowel, it can be assumed that the high frequency energy, including that within the singer's formant region, could be vowel dependent. Strategies to control valleculae volumes are likely to be highly relevant to voice pedagogy practice as well as singing performance.