Hum and buzz
You hear
A low drone at 50 or 60 Hz, or an electrical buzz, sits under your voice.
Hum is electrical: power wiring, a ground loop or a charger reaching the audio path. Fix the cables and power before the settings.
Likely causes, in order
Check them top to bottom. The room and the mic come first because no setting can remove what a closer mic or a closed door would.
| 01 · Layer | 02 · Likely cause | 03 · Fix |
|---|---|---|
| 01 · Mic | A ground loop: two or more connected devices give the audio more than one path to ground | Disconnect the other devices in your audio chain one at a time until the hum stops; a ground loop isolator can fix the one you find ground loop |
| 02 · Mic | The laptop charger, or a third-party power supply, puts electrical noise into a USB mic or interface | Unplug the charger and listen; if the hum stops, run on battery for the call or use the computer maker's own power supply charger |
| 03 · Mic | A USB hub, or the port itself, adds power noise | Plug the mic straight into the computer, and try a USB-C port instead of USB-A, or the other way round direct USB |
| 04 · Mic | Audio cables run alongside power cables, power bricks or lighting cables | Move audio cables away from power cables and bricks, and use the shortest cable that reaches cable path |
| 05 · App | Nothing in the call is filtering a steady hum while you track down the cause | Turn on the app's noise suppression for now, then fix the power path so the filter has less to do stopgap |
By app
- Zoom
- Zoom describes its Low suppression level as blocking low levels of persistent background noise. Auto, the default, adds reduction only when it detects noise.
- Microsoft Teams
- In the Teams iPhone app, Low suppresses low levels of persistent background noise and High suppresses all background sound that isn't speech.
- Google Meet
- Meet's noise cancellation targets sounds that aren't speech; if you need other sounds such as music to come through, Google says to turn it off.
- Discord
- Krisp, Discord's noise suppression, removes background noise that isn't a human voice. For a headset or USB mic, Discord's troubleshooting guide also suggests trying different USB ports.
Check it with the test
The test checks for mains hum on its own. Stay quiet in the first step: if Hum shows 50 or 60 Hz, the test found a peak at that frequency at least 12 dB above the bands beside it. Unplug the charger or the hub and run it again to find the source.
Run the noise test →Questions
Q.01Why 50 Hz in some places and 60 Hz in others?
That is the frequency of the mains power. Audacity's manual gives 60 Hz for North America and 50 Hz for the United Kingdom and most other countries. Recorded hum often brings harmonics above that frequency as well.
Q.02The hum only happens on one computer. What does that mean?
Focusrite suggests trying another computer or room. If the hum goes away elsewhere, the computer's power supply or parts, or the building's wiring, are the likely source.
Q.03Can noise suppression remove hum?
Often, because hum is steady. Browser noise suppression is described as removing background noise and equipment hum. Removing the cause is still better: Audacity notes that reducing noise usually adds some distortion to what is left.
Related problems
Checked against
Vendor help pages and manufacturer guides, last checked :
- manual.audacityteam.org · Notch Filter (Audacity Manual)
- manual.audacityteam.org · Noise Reduction (Audacity Manual)
- support.focusrite.com · Why Is There Unwanted Hum/Noise in My Monitors?
- help.rode.com · USB Microphone Noise Troubleshooting
- developer.mozilla.org · MediaStreamTrack: getSettings() Method
- support.zoom.com · Setting Up Professional Audio for Zoom Meetings
- support.microsoft.com · Reduce Background Noise in Microsoft Teams Meetings
- support.google.com · Filter Out Noise from Your Meeting on Google Meet
- support.discord.com · Krisp FAQ
- support.discord.com · Discord Voice and Video Troubleshooting Guide