# Ground Loop Diagnoser

Diagnose electrical hum contamination in recordings: 50/60 Hz mains family with harmonic profile, ground-loop vs PSU-buzz classification, and a recommended repair chain.

> Canonical page: https://elysiatools.com/en/tools/audio-ground-loop-diagnoser

- **Category:** Media

- **Keywords:** ground loop, mains hum, 50hz, 60hz, buzz, harmonics, goertzel, electrical interference, hum removal, band reject notch, psu noise, audio diagnostics

## Overview

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.

## Inputs

- **Audio recording** (file)
- **Mains frequency** (select)

## When to use

- Location or studio audio contains an audible, steady low-frequency hum or buzzing sound.
- You need to verify whether electrical interference stems from a 50 Hz or 60 Hz mains power system.
- You want to determine if the culprit is a ground loop or a switch-mode power supply before applying corrective EQ or physical troubleshooting.

## How it works

- Upload any audio recording up to 100 MB and select auto-detection or force a 50 Hz or 60 Hz mains base frequency.
- The tool applies targeted Goertzel filters across fundamental and harmonic bins to measure peak prominence above the local noise floor without mistaking musical bass notes for electrical noise.
- Harmonic decay, odd-versus-even dominance, 2-second block variance, and inter-channel correlation are calculated to classify the issue as ground-loop hum, PSU buzz, mild hum, or clean audio.
- An interactive HTML report is generated containing a harmonic bar chart, presence timeline, physical checklist recommendations, and an exact-tuned FFmpeg band-reject notch filter command.

## Use cases

- Diagnosing persistent AC hum in location film dialogue tracks recorded near stage lighting or generators.
- Evaluating studio multitrack recordings to pinpoint whether audio interfaces or outboard gear suffer from ground loops or faulty power bricks.
- Extracting surgically targeted notch filter frequencies for automated audio restoration pipelines.

## Frequently asked questions

### How does the tool distinguish between ground loop hum and PSU buzz?

Ground loop hum exhibits a strong fundamental frequency with smoothly decaying odd harmonics, whereas power supply buzz shows dominant even harmonics from full-wave rectification.

### Can low musical bass notes trigger a false positive?

No, each probe measures spectral prominence relative to immediate neighboring bins, preventing broad musical bass tones from registering as narrow electrical spikes.

### What does inter-channel correlation indicate in the report?

High correlation indicates common-mode electrical noise entering both channels identically, confirming wiring or ground issues rather than acoustic background noise.

### How do I apply the suggested repair chain?

Copy the generated FFmpeg command containing tailored band-reject notch filters into your terminal or post-production workflow to surgically attenuate the detected frequencies.

### Which audio formats and file sizes are supported?

Standard audio file formats are accepted with a maximum upload file size of 100 MB.

## Related tools

- [Audio Band-Reject Filter](https://elysiatools.com/en/tools/audio-band-reject-filter): Remove a specific band of frequencies
- [Classroom Recording Cleaner](https://elysiatools.com/en/tools/audio-classroom-recording-cleaner): Clean lecture recordings with speech-focused EQ, hum reduction, peak control, and optional long-silence trimming.
- [Audio Mouth Click Finder](https://elysiatools.com/en/tools/audio-mouth-click-finder): Detect-style repair for lip smacks, saliva clicks, mouth ticks, and small voice-over clicks.
- [Audio Notch Filter](https://elysiatools.com/en/tools/audio-notch-filter): Remove a very narrow frequency band (e.g., hum)
- [Spectral Denoiser](https://elysiatools.com/en/tools/spectral-denoiser): Reduce broadband noise with a spectral filter chain
- [Audio Click Removal](https://elysiatools.com/en/tools/audio-click-removal): Remove clicks and pops from vinyl recordings
- [Audio Decrackler](https://elysiatools.com/en/tools/audio-decrackle): Remove crackles and subtle impulsive noise from audio files. Ideal for restoring old recordings, cassette tapes, and digitized vinyl with surface noise
- [Audio Filler Word Removal Map](https://elysiatools.com/en/tools/audio-filler-word-removal-map): Combine a timestamped transcript with the audio to mark filler words (um, uh, 嗯, 那个…) and optionally mute or remove them.

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