Table 5 The description of temporal and spectral properties of calls

Call rate

Number of calls per minute. It is inverse of call period.

Call duration

Duration between start of the first pulse and end of the last pulse of a call

Rise time

Time between start of the first pulse and spike of peak amplitude in the pulse of highest amplitude.

Fall time

Time between spike of peak amplitude in the pulse of highest amplitude and end of the last pulse in a call.

Low peak frequency (Hz)

Maximum frequency in the range of 0.3–0.8 kHz (low peak) determined over the duration of a call (FFT size = 1024 pts., Hanning window, 43.1 Hz resolution).

High peak frequency (Hz)

Maximum frequency in the range of 0.8–3.0 kHz (high peak) determined over the duration of a call FFT size = 1024 pts., Hanning window, 43.1 Hz resolution).

Delta power (dB)

The maximum power in a call

FM of low frequency (Hz)

Difference in the low frequency between last 12 ms and first 12 ms window of the call measured by producing a power spectrum from selection spectrum function (FFT size = 512 sample size, Hanning window, 43.1 Hz resolution) of Raven Pro Bioacoustics Research Program software over the duration of the entire call

FM of high frequency (Hz)

Difference in the high frequency between last 12 ms and first 12 ms window of the call measured by producing a power spectrum from selection spectrum function (FFT size = 512 sample size, Hanning window, 43.1 Hz resolution) of Raven Pro Bioacoustics Research Program software over the duration of the entire call

Dominant harmonic

Energy concentrated in separated and evenly spaced frequency of the wave of the longest wavelength