extract_boundary_pulse: Extract boundary points for each pulse
In ThierryO/soundcluster: Extract sounds from WAV files and cluster them

Extract boundary points for each pulse

1 2	extract_boundary_pulse(spectrogram, threshold_amplitude = 10, min_peak_amplitude = 30, amplitude_step = 5)

`spectrogram`	a `soundSpectrogram` object
`threshold_amplitude`	relevant regions have an amplitude above the `threshold_amplitude`. Defaults to 10 dB.
`min_peak_amplitude`	the maximum amplitude in a relevant region must be above `min_peak_amplitude`. Defaults to 30 dB.
`amplitude_step`	the step size in which the threshold amplitude is increased. Defaults to 5 dB.