Table 2.

Classification of the 15 different syllables types and grouping into 3 different syllable classes used in this study. Ambiguous syllables or other sounds were verified by acoustical inspection

Syllable shape	Syllable label	Syllable type	Syllable class	Definition	References
(<  5 ms)	us	ultrashort	Short syllables	Syllables < 91 kHz that are < 5 ms regardless of the shape	[39]
(<  10 ms)	s	short		Syllables < 91 kHz that are < 10 ms regardless of the shape	[26]
	f	flat	Simple syllables	Syllables < 91 kHz with < 5 kHz frequency modulation	[26]
	d	down		Syllables < 91 kHz that decreases in frequency for > 5 kHz	[26]
	up	up		Syllables < 91 kHz that increase in frequency for > 5 kHz	[26]
	u	u-shaped		Syllables < 91 kHz that first decrease, and then increase in frequency for > 5 kHz each	[26]
	ui	u-shaped inverted		Syllables < 91 kHz that first increase, then decrease in frequency for > 5 kHz each	[26]
	c	complex	Complex syllables	Syllables < 91 kHz that contain ≥2 directional changes in frequency and > 5 kHz modulation of frequency	[26]
	c2	complex 2		Syllables < 91 kHz consisting of 2 elements separated by 1 frequency-jump without time separation	[20]
	c3	complex 3		Syllables < 91 kHz consisting of 3 elements separated by 2 frequency-jumps without time separation	[20]
	c4	complex 4		Syllables < 91 kHz consisting of 4 elements separated by 3 frequency-jumps without time separation	Added category for our classification
	c5	complex 5		Syllables < 91 kHz consisting of ≥5 elements separated by ≥4 frequency jumps without time separation	Added category for our classification
	h	harmonic		Syllables < 91 kHz that have an harmonic element	[26]
(>  91 kHz)	uh	ultra high		All syllables > 91 kHz regardless of the shape	[23]
	uc	unclassified		Syllables that do not fit any other of the 14 categories due to background noise or that lack clearly defined spectrographic features (shape)	[40, 41]