Separating anthropogenic from natural sound in a park setting

This paper is a continuation of a study with the National Park Service to detect and separate natural and anthropogenic sound in a park setting. Last year, an algorithm was written to detect anthropogenic tones, because virtually all anthropogenic sound contains tones less than one 1KHz. By comparing each frequency to the surrounding third octave band, the algorithm detects almost all anthropogenic sounds. However, this method does not work for jet aircraft, because of their broad band sound when flying at altitude, not tones. This year, an algorithm was developed to detect jet aircraft, by comparing natural and anthropogenic sound over time as opposed to over frequency. The algorithm finds average equivalent sound level (LEQ) over a day and then removes anomalous peaks from the original sound recording. The program then subtracts the LEQ from the entire file, and the remaining sound is marked as probable jet aircraft sound. If the sound is present for a long enough duration, it is recorded as a jet sound.