Call types	Description
short	duration ≤5 msec and frequency range ≤6.25 kHz
simple	duration >5 msec and frequency range ≤6.25 kHz (flat), or frequency modulation in only one direction (upward or downward) with frequency range >6.25 kHz
complex	frequency modulations in more than one direction and frequency range >6.25 kHz (modulated), or inclusion of one or more additional frequency component (harmonic or non-linear phenomena, but no saturation) but no constraint on frequency range (complex)
frequency jumps	inclusion of one jump (one frequency jump) or more jumps (frequency jumps, others) in frequency without time gap between the consecutive frequency components, with (mixed) or without any noisy part within the pure tone call
unstructured	no pure tone component identifiable; “noisy” calls