Fig. 3

Classification results. a) Results of the first subject. For each condition, the top left box plot shows the distribution of envelope values of all OPMs across all time points. The middle line, box bottom and top edges and whiskers indicate the median, the first and third quartiles, and the minimum and maximum, respectively. Using a permutation test, we compared the median values of these distributions, and all pairwise tests led to significant differences with p < 0.001. The boxplot in the middle illustrates the distribution of Z-scored envelope values per channel and condition. For each channel, the left, middle, and right boxes represent the loud high, loud low, and soft high conditions, respectively (Z-scoring was applied across conditions for each channel separately). All channels exhibited significant differences between the medians of the Z-scored envelope distributions (all p-values < 0.001). The top right depicts the confusion chart (total normalized), resulting from a tenfold cross-validated LDA classifier (F1 = 0.66, p < 0.001). The bottom row shows the mean envelope values of the OPM array for each condition. Despite the subtle differences, the LDA classifier was able to distinguish the three phonation conditions from each other. b) Results of the second subject. All statistical tests related to the box plots led to significant differences with p < 0.001. Classification using LDA resulted in F1 = 0.59, p < 0.001.