Representation of the discriminant functions (DFs) projected into the spectrographic space for the SPC parameters.

<p>The first 3 DFs, obtained from the SPC parameters, are shown for females (left) and males (right). Each row indicates the type of dataset used to perform the DFA: each distance taken separately for 2 m, 64 m and 256 m (first 3 rows) and all distances taken into account (bottom row). As examples, on DF1 at 2 m for females and DF2 at 64 m for males, full arrows show positive frequency bands (red) and dashed arrows show negative bands (blue). This representation enables a description of the most important features in the spectrogram that can be used to discriminate between individuals at various distances.