Modulation rate PCA resulting loading patterns.

Mean rectified loading patterns for the first 3 principal components obtained for spectral bands 1–5 in the modulation rate PCA, averaged over all speech samples. In (a, left), the PC loading patterns for each spectral band are overlaid. In (b, right), the same loading data is separated by PCs into subplots for clarity. For both (a) and (b), the 5 different colours indicate the 5 different spectral bands. The linestyle (solid, dashed or dotted) indicates the PC number. Coloured circles show local troughs in loading that indicate potential boundaries between modulation rate bands (also marked on the x-axis with vertical dotted lines). The coloured diamonds show local peaks in loading that indicate clusters of modulation rate channels that show strong covariance in temporal patterning. The colour of each circle or diamond reflects its spectral band, following the main colour scheme.