Updated October 2026 · Audio repair and clean-up
Find the source of the hum first, because most hum comes from power cables, lights, a computer or a bad ground. Fix it there if you can. If hum remains, use a narrow notch filter at the hum frequency, and listen to make sure the voice has not lost its warmth.
Hum is a steady low tone that sits under a recording, often at 50 or 60 hertz depending on the mains supply, with harmonics above it. It is one of the most common problems in home recordings and one of the easiest to fix if you find the cause. Filtering helps, but the best fix is removing the source.
Turn things off one at a time and record a few seconds of silence after each change. Common sources are a laptop charger, a light dimmer, a fridge, a USB hub, a monitor or a poor audio cable. A microphone cable run beside a power cable can pick up hum too. Once the hum drops when something is switched off, you know the cause.
If hum remains, a notch filter at the hum frequency and its harmonics can reduce it. Keep the notch narrow, so the voice keeps its warmth. Wide filters remove the body of the voice as well. Listen carefully, because a notch that is too wide makes the speech sound thin and hollow.
Play the processed file on headphones, then on a phone speaker. Check the quiet pauses in particular, since hum shows most clearly when the voice stops. The cleanup guide shows how to apply light cleanup without over-processing.
A filter cannot remove hum that overlaps the voice closely, and heavy filtering damages the sound. If the hum is strong, fix the cause and re-record where you can. Clean recordings are always easier to finish than repaired ones.
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Usually a power source, a cable run beside power, or a poor ground. Find the source by switching things off one at a time.
Often you can reduce it a lot. Complete removal is harder, especially when hum overlaps the voice.
Some can, but a targeted notch is usually more precise. Check the result on the pauses.
Mains frequency differs by country, which is why hum is often at 50 or 60 hertz. The cause is still a nearby source.
