# Auditory Perception of Impulsiveness and Tonality in Vocal Fry
## 3 Results
### Impulsiveness, Tonality, and Naturalness Predicted from Glottal Parameters  
Table 3 lists all-listener weights of the linear regression models regarding perceived impulsiveness, tonality, and naturalness as functions of Fo, Qo, and Qs (Experiment 1) and Fo, \(\Delta\)Fo, Qo, and \(\Delta\)Qo (Experiment 2). Parameters Fo, \(\Delta\)Fo, and Qo are shown to significantly affect perceived impulsiveness with equal effect directions as in binary fry (cf. Table 1). The context parameter \(\Delta\)Fo, which was marginally non-significant when vocal fry was rated binarily (\(p=0.06\)), is significant here when the 7-point Likert scale is used to reflect impulsiveness. Tonality ratings are shown to be inversely related to perceived impulsiveness. Parameters Fo, Qo, and \(\Delta\)Fo significantly affect perceived tonality in directions opposite to perceived impulsiveness. A decrease in Fo significantly decreases perceived tonality. The decrease in pitch strength with a decrease in Fo accords with previous findings for frequencies larger than 120 Hz [26]. Here, we show that the inverse relation of Fo and pitch strength is also observed for Fo values below 120 Hz. The tonality decreases with decreasing open quotient Qo, which agrees with a previous study [26] in which sinusoids were reported to have a larger pitch strength than complex tones. Indeed, decreasing the open quotient increases the magnitude of the overtones, making the signal less sinusoidal. However, the effect of Qo is smaller than the effect of Fo. Tonality and frequency difference \(\Delta\)Fo are inversely related. This may be interpreted as the tonality ratings being biased owing to the listeners' inability to ignore the short-term context. For Experiment 1, the perceived naturalness of the stimuli significantly increases with frequency Fo and open quotient Qo. This may reflect the difficulty of synthesizing vocal fry that sounds convincingly natural. An indication is that none of the medians of the naturalness ratings reaches its maximum of +3 (see Figure 11). Figure 12 shows the ROC curves for the prediction of binary fry from perceived impulsiveness ratings. The purpose is to show that perceived impulsiveness is a proxy for perceived binary fry. The curves are similar for the two experiments, with large AUC values of 0.96 and 0.91 for Experiments 1 and 2, respectively. Thus, perceived impulsiveness may be interpreted as a proxy for perceived binary fry. The optimal cutoff threshold is 0 for Experiment 1, which is the center of the 7-point Likert scale. The model's sensitivity (i.e., true positive rate) is smaller for Experiment 2, for which the optimal threshold is 1. Similarly to the ROCs that report the prediction of binary fry from Fo (Figure 8), the AUC is larger for Experiment 1 than for Experiment 2. Finally, both AUC values increased when the impulsiveness ratings of individual listeners were replaced by majority votes (AUC = 0.99 and AUC = 0.97 for Experiments 1 and 2, respectively). \begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**Impulsiveness**} & \multicolumn{2}{c}{**Tonality**} & \multicolumn{2}{c}{**Naturalness**} \\ \cline{2-7}  & **Exp. 1** & **Exp. 2** & **Exp. 1** & **Exp. 2** & **Exp. 1** & **Exp. 2** \\ \hline Const. & 0.48 & 0.31 & \(-\)0.30 & 0.34 & \(-\)0.21 & 0.32 \\ Fo & \(-\)1.75 & \(-\)1.21 & 1.63 & 1.03 & 1.27 & 0.64 \\ \(\Delta\)Fo & n.a. & 0.22 & n.a. & \(-\)0.34 & n.a. & \(-\)0.25 \\ Qo & \(-\)0.09 & \(-\)0.24 & 0.32 & 0.21 & 0.18 & \(-\)0.04 \\ \(\Delta\)Qo & n.a. & \(-\)0.03 & n.a. & \(-\)0.03 & n.a. & \(-\)0.02 \\ Qs & 0.01 & n.a. & \(-\)0.06 & n.a. & 0.03 & n.a. \\ \hline \end{tabular}  
* Coefficients that differ from 0 significantly (\(p\leq 0.05\), Bonferroni-Holm corrected) are highlighted in gray.  
\end{table} 
Table 3: All-listeners’ z-normalized coefficient estimates of linear regression models of perceived impulsiveness, tonality, and naturalness *.