| Absolute frequency parameter |
| Start, mid, finish frequency |
Fundamental frequency at the start, at the middle, and at the end of the rumble (Hz). |
| Min and max frequency |
Lowest and highest measured frequency of the fundamental (Hz) |
| Mean frequency |
Calculated as average frequency across the fundamental |
| Mean1st, 2nd and 3rd Third |
mean fundamental frequencies of first, second, and third part of the sound segment (Hz) |
| Temporal parameters |
| Duration |
Temporal distance of rumble measured in seconds (s) |
| Min and max frequency loc |
Location of the minimum and maximum frequency on the fundamental contour (s). |
| TimeMin/Max |
Temporal distance between min and max frequency (s) |
| Shape and contour parameters |
| COFM - Coefficient of frequency modulation |
Calculated variable that represents the amount and magnitude of frequency modulation across a rumble, computed by summing the absolute values of the difference between sequential frequencies divided by 10,000. |
| Jitter Factor (Mitani and Brandt 1994) |
Calculated variable that represents a weighted measure of the amount of frequency modulation, by calculating the sum of the absolute value of the difference between two sequential frequencies divided by the mean frequency. The sum result is then divided by the total number of points measured minus 1 and the final value is obtained by multiplying it by 100. |
| Frequency variability index (Mitani and Brandt 1994) |
Calculated variable that represents the magnitude of frequency modulation across a rumble, computed by dividing the variance in frequency by the square of the average frequency of a rumble and then multiplying the value by 10. |
| Start, middle, and final slope |
Calculated as (Frequency 20-Frequency 1)/(Time 20-Time 1) (Frequency 40-Frequency 20)/(Time 40-Time 20) (Frequency 60-Frequency 40)/(Time 60-Time 40) |
| Filter-related features |
| Formant 1 |
First spectral peak of the LPC smoothed spectrum in the range of 0 to 500 Hz (model order 8) |
| Formant 2 |
Second spectral peak of the LPC smoothed spectrum in the range of 0 to 500 Hz (model order 8) |
