Electrical hum is one of the most common contaminants in location and studio recordings, and it has a fingerprint. This tool decodes your audio and probes the mains frequency families the way an engineer reads the spectrum: exact-frequency Goertzel probes at 50 Hz and 60 Hz plus harmonics up to the 8th, each measured as prominence above the local spectral floor (the neighboring bins), so a big low-frequency musical note does not masquerade as hum. With mains set to auto, the stronger harmonic FAMILY wins - a recording whose energy sits at 100/200/300 Hz belongs to the 50 Hz family, one at 120/240/360 Hz to 60 Hz. The harmonic shape drives the diagnosis the classic way: a strong fundamental with smoothly decaying, odd-dominant harmonics is ground-loop / transformer hum (steady, sitting there with volume down, changing when you touch gear or unplug one cable); a buzz where the rectifier family - the 2nd/4th harmonics, 100/120 Hz and up - dominates over the fundamental points at power-supply and rectifier noise; weak prominence is mild hum; none is clean. The report also measures steadiness (hum level variance across 2-second blocks - ground loops are famously steady), reports both channels separately with their correlation (common-mode hum hits both channels nearly identically, a telltale of electrical rather than acoustic pickup), and renders the harmonic profile as a bar chart plus a hum-presence timeline. Finally it hands you a repair kit: an FFmpeg chain with band-reject notches tuned to the exact harmonics found (copy it into your own processing or the noise profile extractor workflow), and the physical checklist audio engineers actually use - star-ground all gear to one outlet, separate audio from power runs, lift the shield at one end of balanced runs or use a DI/isolation transformer, and suspect dimmers and switch-mode supplies when the buzz family dominates. Diagnosis is measurement; the fix for a true ground loop is electrical.