While it is relatively easy to determine arcing, tracking or corona by the sound pattern, there can be occasions where it may prove confusing. It may be possible that a strong buzzing sound related to corona might in fact be nothing more than mechanical looseness. Both Spectral analysis and Time Domain can be a useful tools in analyzing electric emissions. Since all Ultraprobe instruments heterodyne ultrasound down into the audible range, either the headphone jack or the Instrument itself (the Ultraprobe 10000) may be used to record sounds. You must use a suitable recording device thathas a suitable bandwidth in the lower frequencies.