Table 1.

Acoustic properties of the three stimulus categories.

Property	Human voices	Animal sounds	Sounds of musical instruments	p
Intensity mean (db)	76.3	73.5	76.8	0.156
F0 mean (Hz)	168.6*	301.9	246.5	0.001
F0 SD (Hz)	35.5*	62.6	61.2	0.001
Jitter local %	2.8	4.1	2.3	0.015
Shimmer local %	12.4	15.9	11.7	0.010
Harmonics-to-noise ratio (db)	9.5	6.0	12.9	0.003

Asterisks: mark those acoustic properties by which human voices differed unidirectionally both from animal sounds and musical instruments.