## 3 Results  
The mean (\(\pm 1\) SE) VD thresholds based on the F0, formants, and combined (F0 + formants) cues in quiet and in noisy conditions for the children and the adults are shown in Table 1. Because there was no significant effect of measurement and no significant interactions with measurement (\(p>0.05\)), the two measurements for each acoustic cue, under each condition (quiet; noisy), were averaged. Figure 2 presents box whisker plots for mean measurements 1 and 2 within each group and condition, separately for each acoustic cue. A repeated measures (RM) ANOVA was conducted with age group (adults, children) as the between-subject variable and condition (quiet, noise) and acoustic cue (F0, formants, combined) as the within-subject variables. The results showed significant main effects of the condition (F(1,38) = 32.450 \(p<0.001\), \(\eta^{2}\) = 0.461) and acoustic cue ([2,38] = 61.840 \(p<0.001\), \(\eta^{2}\) = 0.619), with no significant main effect of the age group (F(1,38) = 3.318 \(p=0.077\)). There were significant acoustic cue X age group (F(2,38) = 4.608 \(p=0.013\), \(\eta^{2}\) = 0.108) and acoustic cue X condition (F(2,38) = 19.188 \(p<0.001\), \(\eta^{2}\) = 0.336) interactions. Post hoc analyses of the interactions are shown in Table 2. In general, the findings indicated that (1) the addition of background noise deteriorated formant VD thresholds for both age groups, and (2) the children exhibited inferior F0 VD thresholds compared to the adults,  
Figure 1: The experimental design. All participants underwent a hearing test and completed 12 VD assessments: 6 in quiet conditions, 2 with each cue (F0, formants, combined), and 6 in background noise, 2 with each of the cues. The order of presentation of voice cues and sentences for the VD test was counterbalanced between participants, with half of the participants first tested in noisy conditions and the other half in quiet conditions. Prior to the testing phase, a brief VD familiarization exercise was carried out with F0 cues in quiet conditions. SRTn = speech reception thresholds in noisy conditions, VD = voice discrimination. Combined = F0 + formants. irrespective of the testing conditions, with comparable formant and F0+formant VD for both age groups. \begin{table}
\begin{tabular}{c c c c c} \hline  & **Quiet** & \multicolumn{2}{c}{**Noise**} \\ \hline  & **Adults** & **Children** & **Adults** & **Children** \\ \hline F0 1 & 0.88 & 1.66 & 0.99 & 1.78 \\  & (0.12) & (0.38) & (0.12) & (0.45) \\ \hline F0 2 & 0.72 & 1.86 & 0.93 & 1.28 \\  & (0.08) & (0.38) & (0.11) & (0.32) \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} Formant 1 \\ \end{tabular} } & 0.62 & 0.85 & 1.32 & 1.39 \\  & (0.07) & (0.14) & (0.13) & (0.35) \\ \hline \multirow{2}{*}{
\begin{tabular}{c} Formant 2 \\ \end{tabular} } & 0.60 & 0.76 & 1.20 & 1.25 \\  & (0.07) & (0.12) & (0.13) & (0.31) \\ \hline \multirow{2}{*}{Combined 1} & 0.42 & 0.59 & 0.57 & 0.76 \\  & (0.03) & (0.07) & (0.07) & (0.19) \\ \hline \multirow{2}{*}{Combined 2} & 0.43 & 0.46 & 0.58 & 0.80 \\  & (0.06) & (0.06) & (0.06) & (0.20) \\ \hline \end{tabular}
\end{table} 
Table 1: Mean (\(\pm 1\) SE) voice-discrimination thresholds (in semitones) based on the F0, formants, and combined (F0 + formants) cues in quiet and noisy conditions for children (\(n=16\)) and adults (\(n=24\)). \begin{table}
\begin{tabular}{c c c c} \hline  & **F0** & **Formants** & **Combined** \\ \hline Adults and children & Noise = quiet & Noise \textgreater{} quiet *** & Noise \textgreater{} quiet *** \\ \hline Quiet and noise & Children \textgreater{} adults * & Children = adults & Children = adults \\ \hline \end{tabular}
\end{table} 
Table 2: Results of the post hoc analyses of the interactions of acoustic cue X age group (first row) and acoustic cue X condition (second row). * = \(p<0.05\), *** = \(p<0.001\). It is important to note that ‘\(=\)’ indicates no significant difference between the two cues, and ‘\(>\)’ indicates higher (worse) thresholds for the cue indicated on the left.