Table 4 Descriptions of the variables that were used in the CART and RF.
Variable name | Unit | Abbreviation | Description |
|---|---|---|---|
Lower frequency* | Hz | Lower | Lowest frequency of the call |
Upper frequency* | Hz | Upper | Highest frequency of the call |
Frequency range | Hz | Range | Ratio of lower to upper frequency |
Duration* | s | Dur | Length of the feature box |
Bandwidth* | Hz | Band | Height of the feature box |
Median frequency* | Hz | Median | The frequency at which 50% of the energy is to either side |
Frequency of peak overall intensity* | Hz | Peak | The frequency with the greatest energy/amplitude in the feature box |
Amplitude modulation rate* | Rate | Ampmod | Dominant rate of amplitude modulation |
Frequency modulation rate* | Rate | Freqmod | Dominant rate of frequency modulation |
Overall entropy* | Bits | Entropy | Measure of how evenly energy is distributed across the frequencies |
Upsweep fraction* | % | Upsweep | Fraction of time that the median frequency in one time block is greater than the preceding time block |
Bout | Bout | Number of the same call type in sequence in a discrete period of time (< 2 s separation between instances) | |
Start frequency | Hz | Start | Frequency at the beginning of the call measured on the fundamental frequency or lowest harmonic |
End frequency | Hz | End | Frequency at the end of the call measured on the fundamental frequency or lowest harmonic |
Frequency trend | Hz | Trend | Ratio of start to end frequency |
Number of inflection points in the peak frequency contour | Inflection | Count of the number of times the slope of the peak frequency contour changes |
