Formal definition:
that is, AM is simply the overall time-derivative power across all frequencies within a range. Units of AM are 1/t, SAP2 does not scale AM, and time units are defined by the ‘advance window’ parameter. Amplitude modulation captures changes in the amplitude envelope of sounds. It is positive in the beginning and negative at the end of each sound, with the sound unit being either a syllable or a change of vocal state within a syllable.