Table 1 Description of measured acoustic parameters

Call duration [ms]

Time between the onset and the offset of a call.

ICI [ms]

Time between the offset of a call and the onset of the successive call.

Peaktime [ms]

Time between the onset and the maximum amplitude of a call.

MeanF0 [Hz]

Mean fundamental frequency of a call.

MinF0 [Hz]

Minimum fundamental frequency of a call.

MaxF0 [Hz]

Maximum fundamental frequency of a call.

SDF0 [Hz]

Standard deviation of the fundamental frequency of a call.

Peak [Hz]

Frequency with maximum energy over a call.

MeanF1 [Hz]

Mean frequency of the first formant of a call.

SDF1 [Hz]

Standard deviation of the first formant frequency of a call.

BWF1[Hz]

Bandwidth of the first formant frequency of a call.

MeanF2 [Hz]

Mean frequency of the second formant of a call.

SDF2 [Hz]

Standard deviation of the second formant frequency of a call.

BWF2 [Hz]

Bandwidth of the second formant frequency of a call.

MeanF3 [Hz]

Mean frequency of the third formant of a call.

SDF3 [Hz]

Standard deviation of the third formant frequency of a call.

BWF3 [Hz]

Bandwidth of the third formant frequency of a call.

F2–F1 [Hz]

Difference between the mean of the second and the first formant frequency.

Consistency

Mean maximum correlation of power spectra of successive 25 ms time steps of a call.

Cepstral peak [V]

Value of the peak at the fundamental period of a cepstrum for the middle 10 ms of the call.

Voiced [%]

Percentage of voiced frames of a call.

MaxHNR [db]

Maximum harmonic-to-noise ratio of a call.