Table 1. Description of the acoustic features measured.
| Variable | Description |
|---|---|
| Q1Freq | Frequency that divides the spectrum into two frequency intervals containing 25% and 75% of the energy (Hz) |
| Q3Freq | Frequency that divides the spectrum into two frequency intervals containing 75% and 25% of the energy (Hz) |
| IQRBW | Difference between the 1st and 3rd Quartile Frequencies. Q3Freq—Q1Freq (Hz) |
| AggEntropy | Aggregate entropy: measurement of the disorder in a sound by analysing the energy distribution within a selection. Higher entropy values correspond to greater disorder in the sound, whereas a pure tone with energy in only one frequency bin would have a value of zero [40] |
| AvgEntropy | Average entropy: average of the entropy for each frame in the selection [40] |
| CentFreq | Frequency that divides the spectrum into two frequency intervals of equal energy (Hz) |
| Freq5 | Frequency that divides the spectrum into two frequency intervals containing 5% and 95% of the energy (Hz) |
| Freq95 | Frequency that divides the spectrum into two frequency intervals containing 95% and 5% of the energy (Hz) |
| BW90 | The difference between the 5% and 95% frequencies. Freq95—Freq5 (Hz) |
| MaxFreq | The frequency at which the maximum amplitude occurs (Hz) |
| AED-M1 | Frequency corresponding to the mean energy density (Hz) |
| AED-SD1 | Standard deviation of the mean energy density (Hz) |
| AED-P1 | Frequency corresponding to the peak of the energy density (Hz) |
AED: acoustic energy distribution (spectral distribution of the energy transmitted by sound via the propagating pressure fluctuations).
1: variables measured using custom made software (see S1 Appendix)