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Plant Classification from Bat-Like Echolocation Signals

Figure 6

Effect of the DFT window length on classification performance.

(A) The area under the ROC curve (AUC) for four different window lengths ranging from 250–2000 µs. Average results are presented together with the blackthorn classification case, in which the effect was most clear. The difference between a 2000 µs window length and the other lengths is significant (P<0.05), whereas the difference between the three other lengths is not. (B) Average spectrograms for a window length of 2000 µs (first row) and a 250 µs one (second row) for the classification task of blackthorn vs. the rest. It can be seen how time information is decreased (i.e. smeared) for the 2000 µs window (first row). This makes separation between the two classes easier with the 250 µs window (second row) even when only examining them visually.

Figure 6