# Development of Parameters towards Voice Bifurcations
## 5 Conclusions  
This paper proposes short-term parameters: the harmonic disturbance factor (HDF) and the biphonia index (BI), both of which are based on the ratio of two tonal frequency contents in the voice signal. The HDF and BI are intended to distinguish Type-I signals from Type-II or Type-III signals. Four cases (one normal, three with pathology) are shown to illustrate the behavior of the measures against a wide range of voicing behaviors, and the HDF and BI have exhibited the intended outcomes. The preliminary analysis of the HDF-based detector of non-Type-I voice signals is also presented, reporting a 99.9% detection rate with fixed a 0.01% false-alarm rate. Potential applications of these parameters towards objective clinical assessment are suggested.  
Conceptualization, T.I. and M.K.; resources, M.K.; methodology, T.I.; software, T.I.; writing--original draft preparation, T.I.; writing--review and editing, M.K., A.J.M., and L.A. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The data for this retrospective study were collected according to the guidelines of the Declaration of Helsinki and approved by the Institutional Review Board of Louisiana State University (IRB#2667, last renewed 2020; IRB#2668, last renewed 2020).  
Informed Consent Statement: Informed consent was obtained from all subjects involved in the study.  
The highspeed endoscopic videos analyzed in this study can be found here: [[https://doi.org/10.5281/zenodo.4928535](https://doi.org/10.5281/zenodo.4928535)]([https://doi.org/10.5281/zenodo.4928535](https://doi.org/10.5281/zenodo.4928535)) accessed on 11 June 2021.  
The authors declare no conflict of interest.  
Appendix A Description of High-speed Videoendoscopy (HSV) Data and Preparation of Glottal Area Waveforms  
The HSV data were collected at Louisiana State University (LSU) (Case 1) and at Our Lady of the Lake Regional Medical Center (OLOL) (all other cases) with a rigid 70\({}^{\circ}\) endoscope (Model 9106, KayPENTAX) paired with an HSV system (Model 9700, KayPENTAX, for Cases 1-3 and Model 9710 for Case 4) and a 300-watt cold light source (CLV-U20, Olympus America Inc., Center Valley, PA, USA). During the recording, patients were instructed to sustain /i/ with comfortable pitch and loudness while the laryngoscope was placed in their oral cavity. All HSV videos are in 8-bit grayscale. For Cases 1-3, the frame rate is 2000 frames-per-second (fps) with frame dimension of 120 pixels wide by 256 pixels high, while Case 4 was captured at 4000 fps with dimension 256 pixels by 512 pixels. The use of the data in the study was approved by the Institutional Review Boards of Louisiana State University and of OLOL.  
Each set of HSV data typically contains two sustained /i/ phonations. A phonation with best view angle and lighting were selected. The glottal area waveforms were extracted from the HSV data following the procedure in [31]. The region growing segmentation algorithm was employed to identify glottal pixels. To initialize the algorithm, a threshold profile over all frames in each recording was manually set so consistent segmentation results were obtained throughout the phonation. The glottal area waveform is a sequence of the number of glottal pixels over all phonation frames. The Case 4 glottal area waveform was then decimated by 2 to reduce its sampling rate to 2000 samples/second to match the rest of the cases. Finally, the unvoiced samples were trimmed from the beginning and end of the glottal area waveforms.