Microphone hum: find what is causing the buzz
Start by checking whether the hum is in your saved recording or only in your speakers. Then change one connection at a time. A low electrical hum needs different checks from a broad background hiss.
First, check where the hum is heard
Save a short recording with a spoken sentence and a pause. Play that same file through headphones, then through a second listening setup. Keep the listening volume comfortable.
| What you observe | What to check next |
|---|---|
| The file hums on both setups | The recording path: microphone, cable, interface and connected devices. |
| Only one pair of speakers hums | The playback path before applying cleanup to the file. |
| Hum starts when another device is connected | That connection and the equipment on either side of it. |
Write down what changed. A quieter second setup narrows the search; it does not identify a faulty part by itself.
Hum, buzz or hiss?
Electrical hum often has a low, steady pitch around 50 or 60 Hz. Higher multiples of that frequency can make it sound more like a buzz. A broad “shhh” has a different character.
A 50/60 Hz peak is a clue, not proof of a ground loop. Nearby electrical fields can also reach microphones. The useful question is which change makes the noise appear, disappear or change level.
Check cables and connected equipment
- Mute the input and speakers before changing audio cables. For an XLR microphone, follow its instructions for switching phantom power off before disconnecting it.
- Try a known-good, compatible cable. For a USB mic, compare a direct computer connection with the hub connection you normally use. Save a new test after each change.
- Move the microphone and its audio cable away from power adapters and lighting equipment. Keep your speaking distance the same for the comparison.
- Remove optional audio connections one at a time, following the equipment instructions. Reconnect them individually and note which connection brings back the hum.
Keep the protective earth on power cables intact. Do not remove a ground pin or open a power adapter to cure hum. Ask the equipment manufacturer about compatible audio isolation if one connection is responsible.
How to read the before-and-after graphs
A spectrogram shows how sound changes over time. Read left to right through the recording; higher frequencies are higher up. Bright yellow means a stronger signal at that frequency. Purple and black show weaker sound.
Yellow does not automatically mean noise: speech can be yellow too. Start with a pause, then follow the sound into the next word. Both panels use the same time, frequency and colour scales and come from the exact audio files below.
| What to compare | What to do with it |
|---|---|
| Straight lines across pauses | Look for steady tonal noise, then use the connection checks above to narrow its source. |
| Bands that move with the words | These may belong to the voice. Do not remove every visible band. |
| The same lines remain after processing | Compare the actual audio and try the targeted cleanup or recording checks below. |
The hiss charts show 0–8,000 Hz; the hum charts zoom in to 0–800 Hz. Open a chart at full size for detail. A black area means little energy on this colour scale, not proof of perfect silence.
Hear three voices with different hum patterns
These English audiobook passages use three real narrators. We added controlled hum to each source, then processed that same recording with Noise Removal. The voice levels are matched for comparison, and the original pauses are retained. The noise was not captured by the narrators’ microphones.
1. Garth Comira — 50 Hz hum with a few higher tones. Compare the low sound in the pause and under the voice.
2. Heather Barnett — stronger 60 Hz hum. Listen to the softer words as well as the background. Keep the headphone volume unchanged.
3. Anders Lankford — a richer 60 Hz buzz with more higher tones. This is the difficult example: the buzz largely remains after processing. Compare it with the first two before deciding whether the result is useful.
In the same short noise-only opening, the measured level falls by about 38 dB, 40 dB and 0.13 dB respectively. Those figures describe that pause in these files; listen to the spoken words too. A quiet pause alone does not establish a clear, natural voice.
Recording credits: The Ashiel Mystery, read by Garth Comira; Sense and Sensibility, read by Heather Barnett; The Age of Chivalry, read by Anders Lankford. Audio from the LibriSpeech collection, adapted by Loudness.ai with added hum, noise reduction, playback alignment and level matching.
Reduce hum in an existing recording
Keep the original file. Try a short passage with speech and a pause, then compare it at the same voice level. If the buzz remains or the voice loses detail, avoid repeatedly processing the whole file.
For steady tonal noise, an audio editor’s narrow notch filter can target the measured frequency. Check the noise-only section for higher multiples too. Cutting a wide band or removing every low frequency can change the voice. Compare and undo changes that make speech worse.
Repeat the test after fixing the source
Record the same sentence and pause again. Match voice volume when comparing the old and new takes, and write down the cable or device change that helped. If the noise returns, that note gives you a useful starting point.
Fixing the source prevents hum from entering the next recording. Software cleanup only works on audio that has already been captured. If an important passage still sounds damaged, a fresh take may be the more useful result.