Extrinsic Laryngeal Muscle Activity and Vocal Economy in Professionally Trained Voices During Vocal Vibrato.

Purpose: The purpose of the present study was to determine the extrinsic laryngeal muscle activity and vocal economy during two different singing conditions (straight-tone- vs vibrato singing) over a physiologically relevant singing range.

Methods: Thirty professional singers or voice coaches participated in the study. The participants sang a sustained /a:/ vowel for approximately 5seconds, once in straight-tone singing conditions and once more in vibrato. The target pitches were C3, F3, A3, C4, F4, A4, and C5. Surface electromyographic (sEMG) measures were performed in the infrahyoid (IH)- and the suprahyoid (SH) muscle region. Contact quotient (CQ), sound pressure level (SPL), and fundamental frequencies were measured to derive the electroglottographic-based vocal economy parameter quasi-output cost ratio (QOCR).

Results: sEMG measures show that IH and SH muscles significantly increased in activity with ascending pitch. IH and SH muscle activity was also significantly higher when singing in vibrato than straight-tone. Moreover, SPL also increased with ascending pitch and when sung in vibrato. CQ increased and QOCR decreased as pitch ascended but did not significantly change when sung in vibrato.

Conclusion: Singing higher pitches was generally associated with higher extrinsic laryngeal muscle activity and lower QOCR values. When comparing two singing conditions, extrinsic laryngeal muscle activity was higher during vibrato, implicating that IH and the SH muscles may contribute to rhythmic pulsations of pitch modulation. Although the QOCR value did not show significant differences between the two singing conditions, a significantly higher SPL during vibrato may offer some acoustical and physiological advantages. Results also indicate that extrinsic muscle activity may not be reliably measure vocal economy.