4.2 Imitation learning stage4.2.1 Perceptual evaluation The results of the perceptual evaluation of the model’s speech output after imitation learning are presented in Figure 6. In comparison, the perceptual evaluation yields a more consistent pattern for MPD than for MPD+APD. In the case of MPD, results show a steady decrease of both intelligibility and speech quality with increased severity. For MPD+APD, the results follow the same trend for noise levels up to 10%, but then the pattern becomes more complicated. For noise levels of 15% and higher, results show an inverse relation between speech quality and intelligibility. Statistical analyses revealed highly significant main effects of noise level/severity on the intelligibility and quality judgments for both deficits [all p values < .001].