## 4 Discussion  
The novel finding of the present study is that background noise had a negative effect on the use of formants for VD, while F0 was less obscured by noise in both children and adults. Specifically, in the quiet condition, children and adults found the formant cues more beneficial for VD compared with F0 cues, whereas in noisy conditions, formant cues did not show this advantage. As a result, a reversed outcome was observed for adults, with F0 becoming the more dominant cue for VD in the presence of noise. For children, noise also obscured formant cues. However, they had difficulty relying on F0 for VD in noisy conditions, probably due to their immature F0 perception, which was already observed in quiet conditions  
Figure 3: Individual discrimination thresholds for children (\(n=16\)) and adults (\(n=24\)) in noisy conditions as a function of their discrimination thresholds in quiet conditions, for each acoustic cue separately. The results of Pearson coefficient correlations for each pair are shown in the colored boxes. in this study and others [47]. The current study also found that: (a) the combination of F0 and formants cues produced the best VD over the provision of a single cue (either F0 or formants) in both listening conditions, reflecting the additive value of the formant cues, even in the noisy conditions; (b) there were significant positive correlations found between VD thresholds in quiet and in noisy conditions, suggesting that much of the VD performance in noisy conditions was related to basic spectral and temporal processing mechanisms. The major finding of this study, that background noise mainly affected formant perception in both children and adults, probably reflects the fact that although the sentences were clearly audible, the noise obscured some of the spectral information contained in the speech stimuli. Because the noise had the same long-term average spectrum as the target sentences, which resulted in a spectral overlap between the target sentences and the noise, it is possible that the listeners had difficulty in identifying the formant peaks in the spectral envelope of the speech signal [43; 61; 62]. Consequently, larger formant differences were required to accurately discriminate between the voices. This explanation is in line with previous studies that showed degraded vowel formant discrimination when there was background noise [27]. In contrast, VD based on F0 appeared to be less affected by the noise, as shown by the fact that no significant differences were found in VD between quiet and noisy conditions when using F0 for both age groups. This finding is in accordance with studies reporting the robustness of F0 extraction in noisy conditions [63], supporting the notion that F0 perception primarily depends on the temporal envelope of the stimuli [25; 26]. Other studies, however, reported the presence of noise to have a detrimental effect on pitch perception [16; 17], in line with the theory that noise reduces subcortical neural synchrony, leading to potential disruption of phase locking mechanisms [64; 65]. This effect could have also compromised F0 perception due to its partial reliance on fine temporal processing of the speech signal [25; 26]. Nonetheless, this potential impact was not observed in the current study, possibly because of the relatively good audibility of the speech signal at the given SNR. A second important finding is that the children showed significantly poorer VD thresholds based on the F0 cues compared to adults in quiet and noisy conditions. This finding aligns with recent reports on poor VD abilities in children compared to adults [9; 21]. Specifically, the finding supports previous evidence indicating that children exhibit non-adult-like F0 discrimination skills until the age of 12 years, while their formant-discrimination abilities reach adult-like levels at approximately 8 years of age [21].