Table 1. Description of acoustic parameters extracted from songs (see Figure 3).
| Robust acoustic parameter | Definition | Specific measurement* |
| Centre Frequency (Hz) | Frequency that divides the selection into two frequency intervals of equal energy† | 1. Entire song |
| 2. 1st half of song | ||
| 3. 2nd half of song | ||
| 4. Long note | ||
| 5. Short note | ||
| 6. Difference between 1st and 2nd half of song | ||
| 1st Quartile Frequency (Hz) | Frequency dividing the selection into two frequency intervals containing 25% and 75% of the energy† | 7. Long note |
| 8. Short note | ||
| 3rd Quartile Frequency (Hz) | Frequency dividing the selection into two frequency intervals containing 75% and 25% of the energy† | 9. Long note |
| 10. Short note | ||
| Inter-quartile Range Bandwidth (Hz) | The difference between the 1st and 3rd Quartile Frequencies | 11. Long note |
| 12. Short note | ||
| Centre Time (sec) | The duration the selection is divided into two time intervals of equal energy† | 13. Long note |
| 14. Short note | ||
| 1st Quartile Time (sec) | The duration that divides the selection into two time intervals containing 25% and 75% of the energy† | 15. Long note |
| 16. Short note | ||
| 3rd Quartile Time (sec) | The duration that divides the selection into two time intervals containing 75% and 25% of energy† | 17. Short note |
| Inter-quartile Range Duration (sec) | Difference between the 1st and 3rd Quartile time | 18. Long note |
*For all parameters except 1–3, mean was calculated for notes within a song.
†
Power values in short-time spectra and frequency bands that compose the spectrogram are summed to generate aggregate power envelopes and spectra, resulting in a power versus time envelope and power versus frequency spectrum, respectively.
The aggregates are normalized and treated as probability density functions with time or frequency being the variate, and density the fraction of the total signal energy. From the distribution function, various measures of central tendency and dispersion are then used to characterize the signal energy distribution in time and frequency. (See [39]).