Table 3 Acoustic parameters.

Dur (s)

Duration of the call

Duration

^{17,18,19,20,21,27,30,39,40,41}

AmpVar (dB/s)

Amplitude variation; cumulative variation in amplitude divided by the total call duration

Amplitude modulation

²⁰

AmpModRate (s-1)

Amplitude modulation rate; number of complete cycles of amplitude modulation per second

^21,28

AmpModExtent (dB)

Amplitude modulation extent; mean peak-to-peak variation of each amplitude modulation

^21,28

Q25% (Hz)

Frequency value at the upper limit of the first quartiles of energy

Spectrum (energy distribution)

^{18,20,21,27,28,30,39,40}

Q50% (Hz)

Spectral center of gravity; frequency value at the upper limit of the second quartiles of energy

^{17,18,19,20,21,27,28,30,39,40}

Q75% (Hz)

Frequency value at the upper limit of the third quartiles of energy

^{18,20,21,27,28,30,39,40}

FPeak (Hz)

Frequency of peak amplitude

^{17,18,20,30,39,41}

Harmonicity

Degree of acoustic periodicity, also called harmonic-to-noise ratio—higher values indicate more tonal calls

Tonality/noise

^{18,19,20,21,28,30,39,40}

WienEntropy

Wiener entropy; spectral flatness of a sound, calculated as the ratio of a power spectrum's geometric mean to its arithmetic mean measured on a logarithmic scale—higher values indicate more noisy calls

^{17,18,27,39,41}