Microphone hum: find what is causing the buzz

First, check where the hum is heard

Use Mic Test to 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. If only the speakers hum, Focusrite’s monitor-hum troubleshooting guide helps you investigate the playback connections.

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; use the microphone hiss troubleshooting guide for that sound. If the sound follows air moving through the room instead, use the fan-noise guide’s placement and airflow checks to investigate that source.

A 50/60 Hz peak is a clue, not proof of a ground loop. Shure’s explanation of microphone hum pickup describes how 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

1. Mute the input and speakers before changing audio cables. For an XLR microphone, follow its instructions for switching phantom power off before disconnecting it.
2. 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.
3. Move the microphone and its audio cable away from power adapters and lighting equipment. Keep your speaking distance the same for the comparison.
4. Sennheiser’s ground-loop troubleshooting guide provides more detail on tracing connected equipment. 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.

A connection log that identifies the next test

Use the rows below as a worksheet. These are possible outcomes to interpret, not measurements of your equipment. Start from the same baseline before each test; otherwise two changes can cancel each other and hide the cause.

Two reductions—and a buzz that remains

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.

Inspect the before-and-after spectrogram

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2. Heather Barnett — stronger 60 Hz hum. Listen to the softer words as well as the background. Keep the headphone volume unchanged.

Inspect the before-and-after spectrogram

Open full-size chart

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.

Inspect the before-and-after spectrogram

Open full-size chart

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.

Reduce hum in an existing recording

Keep the original file. Try Audio Enhancer’s Noise Removal on 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, follow Audacity’s notch-filter instructions to target the measured frequency with a narrow cut. 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.

In Audacity, select a noise-only pause and use Plot Spectrum to locate the peak. Try a narrow notch at that measured frequency, preview, then compare the voice with the unfiltered original. Inspect higher peaks individually. Do not apply a whole series of 50/60 Hz cuts merely because you know your country’s mains frequency.

Repeat the test after fixing the source

Record the same sentence and pause again with Mic Test. 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.