Hum removal
Hum removal cuts the low electrical hum that mains power can leave on a recording. It places a narrow notch at the mains frequency and at each of its multiples, and leaves the sound between the notches alone.
- Where
- Clip tab ▸ Sound ▸ Hum
- Agent tools
set_audio
Remove hum
Section titled “Remove hum”-
Select a clip with sound, and open the Hum section of the Sound tab.
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Tick Remove hum. It starts at 60 Hz, 30 dB deep, with 4 harmonics.
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Set Mains to the frequency where the recording was made: 50 Hz in most of the world, 60 Hz in most of the Americas and parts of Asia.
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If you can still hear the hum, raise Depth or Harmonics.
The other controls are greyed out until Remove hum is ticked. Reset in the section’s header turns hum removal off.
The controls
Section titled “The controls”| Control | What it does | Range | Default |
|---|---|---|---|
| Remove hum | Turns hum removal on. | On or off | Off |
| Mains | The mains frequency where the recording was made. | 50 Hz or 60 Hz | 60 Hz |
| Depth | How far each notch turns the hum down. Quick picks: 12, 24, 30 and 48 dB. | 6 to 60 dB | 30 dB |
| Harmonics | How many notches: the mains frequency and its multiples. Quick picks: 1, 2, 4 and 8. | 1 to 8 | 4 |
At 60 Hz with 4 harmonics, the notches sit at 60, 120, 180 and 240 Hz.
Each notch is about a tenth of the mains frequency wide, whatever its depth, so a notch at 60 Hz is about 6 Hz wide.
Good to know
Section titled “Good to know”- Hum removal runs after the EQ. Its notches appear in the EQ section’s drawn curve, but the EQ’s Bypass doesn’t turn them off.
- Hum removal only reaches the mains frequency and its multiples. For hiss, fans or other steady noise, use Noise Reduction, which comes after it.
- With an action selected, these controls set where the action ends. Depth glides across the action. Mains, Harmonics and turning hum removal on or off change at the action’s end, with no glide.
- Hum removal set on a nest clip has no effect. Open the nest with ⌘↓ and set it on the clips inside.
With an agent
Section titled “With an agent”set_audio sets the same controls through hum, with frequency, depth_db and harmonics. An empty hum turns it on at the defaults and null turns it off. See Tools: clip sound.