How to remove hum in Audacity

Hum is a low, steady tone from mains electricity leaking into your recording: 60 Hz in North America, 50 Hz in the UK, Europe, Africa and most of Asia, plus quieter copies at multiples (120, 180, 240 Hz or 100, 150, 200 Hz). It usually comes from ground loops, cheap cables, laptop chargers or lights on the same circuit. Because it sits at fixed frequencies, you can cut it precisely.

Select a second or two where nobody is speaking. Choose Analyze, Plot Spectrum. Look for tall, narrow spikes at the low end; the first spike is the hum and the others are its harmonics. You can also switch the track to Spectrogram view, where hum shows as bright horizontal lines near the bottom.

Select the whole track (Ctrl+A or Cmd+A). Choose Effect, EQ and Filters, Notch Filter. Set the frequency to 60 (or 50) and the Q to around 10 to 30 so the cut is narrow and leaves your voice alone. Apply it, then repeat at 120 and 180 (or 100 and 150) if the spectrum showed harmonics. Listen after each pass.

Speech has almost nothing useful below about 80 Hz. Effect, EQ and Filters, High-Pass Filter at 80 Hz with a 12 dB per octave rolloff removes rumble and what is left of the base hum. For more control, use the Audacity equalizer.

If a faint buzz remains, select a noise-only section, open Effect, Noise Removal and Repair, Noise Reduction, and click Get Noise Profile. Then select the whole track, open the effect again and apply with gentle settings. See the best noise reduction settings for Audacity to avoid the watery, robotic sound of overdoing it.

If you edit spoken audio every week, finding frequencies gets old. Hilite's background noise removal cleans hum, hiss and fan noise in one step, and you can try it on a single file with the free AI noise reducer.