Objective: Transglottal airflow (TAF) during phonation measured using a pneumotachometer is a valuable index of vocal function. While pneumotachometer-based systems cost thousands of dollars, the Phonation Quotient (PQ) can provide a valid estimate of TAF by dividing the vital capacity (VC) by the maximum phonation time (MPT). However, the PQ is limited by the expense of a spirometer for VC testing. The vortex whistle is a low-cost device that produces an acoustic signal with a frequency directly proportional to the airflow moving through the whistle and can be used for accurate measures of VC. This study examined the relationship between PQ obtained using a low-cost vortex whistle system (VWS) versus the mean TAF in sustained voicing calculated using the Phonatory Aerodynamic System (PAS).

Methodology: Ninety-one typical voice young adults were tested using (1) the PAS, and (2) a VWS comprised of a 3D printed vortex whistle and audio recording and analysis software. Tasks were:
1. Vital Capacity via the VWS: The greatest VC (L) from three elicited trials was used for data analyses.
2. The Maximum Sustained Phonation protocol of the PAS: Maximum phonation time (MPT in s) and mean TAF (L/s) were obtained from three trials. The greatest MPT and the mean TAF across the three trials were used.
3. The PQ was calculated using the VC from the vortex whistle system (VWS) and the MPT from the PAS MPT protocol using the following formula: PQ (L/s) = VC (L)VWS(L)/MPT(s)

Results: TAF estimated using the vortex whistle and PQ correlated significantly and strongly with mean TAF from the PAS at r = 0.794 (p < .001; r2 = 0.630). In addition, the PQ estimated TAF very closely matched pneumotach captured TAF (0.168 L/s vs. 0.171 L/s).

Conclusions: The VC obtained using a VWS can be used to provide a strong estimate of TAF in sustained voicing via the PQ. Because the potential cost of the VWS will be a small fraction of the cost of a pneumotach-based airflow/spirometry system or portable spirometer, the VWS has the capability to expand the use of aerodynamic measures in clinical voice assessment.