Internal soundgen function.
findSyllables(envelope, timestep, threshold, shortestSyl, shortestPause,
mergeSyl)downsampled amplitude envelope
time difference between two points in the envelope (ms)
all continuous segments above this value are considered to be syllables
minimum acceptable length of syllables, ms
minimum acceptable break between syllables, ms.
Syllables separated by less time are merged. To avoid merging, specify
shortestPause = NA
if TRUE, syllable separated by less than
shortestPause will be merged
Returns a dataframe with timing of syllables.
Called by segment.