When you have Arcing, the discharge to ground across an insulator is a high current path over an insulator that does not require a high potential. This is a “burst of energy” that lasts for extended periods of time. It is indicated by the arrow on the right side of the diagram. The “buzzing” Sound that is heard with corona and the initial stages of tracking is not heard with arcing. Only the “bursts” of discharge can be heard. These will be seen as wide peaks in the time series.