# Characterization of the Intelligibility of
## 3 Results
### Characterization of VCV Intelligibility  
Figure 2 shows the mean value of STOI (panel a) and the variance of STOI (panel b) as a function of the SNR for the five sets of VCVs used here. As the STOI is used here as an estimate of intelligibility, the mean and variance are reported as percent values rather than in the range 0-1. Figure 2a shows that there are differences in mean STOI across the five languages, with VCVs in English being, on average, those with the highest estimated intelligibility (highest mean STOI values throughout the SNR range), followed by VCVs in Italian, whereas VCVs in Portuguese were, on average, those with lowest estimated \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**VCVs** & **English** & **French** & **German** & **Italian** & **Portuguese** \\ \hline aba & 0.90 & 0.83 & 0.92 & 0.80 & 0.94 \\ ada & 0.91 & 0.66 & 0.88 & 0.94 & 0.83 \\ afa & 0.96 & 0.95 & 0.90 & 0.96 & 0.89 \\ aga & 0.88 & 0.55 & 0.89 & 0.87 & 0.85 \\ aka & 0.83 & 0.72 & 0.91 & 0.99 & 0.91 \\ ala & 0.98 & 0.83 & 0.80 & 0.70 & 0.85 \\ ama & 0.74 & 0.56 & 0.63 & 0.69 & n.a. \\ ana & 0.75 & 0.59 & 0.67 & 0.88 & n.a. \\ apa & 0.94 & 0.87 & 0.98 & 0.83 & 0.86 \\ ara & 0.91 & 0.78 & 0.79 & 0.86 & 0.78 \\ asa & 0.92 & 0.55 & n.a. & n.a. & 0.75 \\ ata & 0.78 & 0.79 & 0.96 & 0.97 & 0.85 \\ average & 0.87 & 0.72 & 0.72 & 0.86 & 0.85 \\ s.d. & 0.08 & 0.14 & 0.45 & 0.10 & 0.06 \\ range & 0.74 \(\div\) 0.98 & 0.55 \(\div\) 0.95 & 0.65 \(\div\) 0.98 & 0.69 \(\div\) 0.99 & 0.75 \(\div\) 0.94 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Pearson correlation coefficient between STOI and subjective measures. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**VCVs** & **English** & **French** & **German** & **Italian** & **Portuguese** \\ \hline aba & 0.90 & 0.95 & 0.93 & 0.76 & 0.98 \\ ada & 0.88 & 0.76 & 0.93 & 0.98 & 0.93 \\ afa & 0.84 & 0.97 & 0.85 & 0.98 & 0.97 \\ aga & 0.74 & 0.18 & 0.95 & 0.87 & 0.90 \\ aka & 0.81 & 0.58 & 0.92 & 0.99 &  
intelligibility (lowest mean STOI values). English VCVs led, on average, to estimates of intelligibility from about 1% (at +6 dB SNR) to about 8% (at \(-12\) dB SNR) higher compared to VCVs in Italian, which is the second language in terms of intelligibility. Compared to Portuguese, the improvement in intelligibility ranged from about 4% (at +6 dB SNR) to about 13% (at \(-12\) dB SNR). On average, for negative SNRs, the intelligibility of English VCVs was from about 9% to about 10% higher compared to the average of the other languages. Figure 2b shows that the variance of STOI is low, on average, for all five sets of recordings (i.e., below 0.2% on average), suggesting that, in general, the influence of different noise realizations on STOI estimates of VCV intelligibility is limited in all the tested languages. VCVs in English showed the lowest variance and were, therefore, the least influenced by noise, whereas VCVs in Portuguese showed the highest variance of STOI, i.e., from about two to four times that of VCVs in English. Table 4 reports the average, standard deviation, and range of the observed SRT and slope for VCVs in the five languages studied here. On average, the lowest (better) SRTs were obtained with the VCVs in English (i.e., \(-4.86\) dB SNR), whereas the highest (worse) SRTs were obtained with VCVs in Portuguese (i.e., \(-0.85\) dB SNR). Similarly, the slowest slopes were observed, on average, with VCVs in English (i.e., \(2.58\%\)/dB SNR), whereas the fastest slopes were observed with VCVs in Portuguese (i.e., \(3.26\%\)/dB SNR). The Kolmogorov-Smirnov test was conducted to check whether data were normally distributed. As the assumption of normality was not confirmed, the non-parametric Kruskal-Wallis test was performed to assess possible between-language differences in STOI mean and variance, SRTs, and slope.