A voice actor treats the room, tightens the mic technique, and a faint, steady hum is still sitting under every take. It is a common enough moment of confusion that it is worth naming directly: that particular kind of noise, low, constant, unaffected by anything you do acoustically, is very often electrical, and no amount of foam or blankets will touch it, because it is not coming from the air in the room at all.
What a Ground Loop Actually Is
A ground loop happens when two pieces of connected equipment, say an audio interface and a computer, or an interface and a monitor or lamp on the same circuit, are grounded through more than one path at once. The tiny difference in electrical potential between those paths creates a current that has nowhere useful to go, and it shows up in the audio signal as a persistent low hum, typically at the electrical frequency of your region (60Hz in North America, 50Hz in most of Europe and beyond) or its harmonics.
- It is constant, not intermittent. Unlike a fan cycling on or traffic outside, ground loop hum does not come and go with the room; it sits there at a steady level the entire time the circuit exists.
- It often changes when you touch the mic or a cable. A hum that shifts pitch or volume slightly when you grip an XLR connector or touch the mic body is a strong signal pointing toward a grounding issue rather than an acoustic one.
- It frequently correlates with specific device combinations. Hum that appears only when a monitor, a lamp, or a laptop charger is plugged into a particular outlet, and disappears when it is unplugged, is close to a confirmed diagnosis on its own.
A Simple Diagnostic Process
- Record a short test clip with everything in your setup running normally and note the hum.
- Unplug non-essential devices one at a time, monitor, lamp, charger, second computer, re-recording a short test after each change.
- If the hum disappears when a specific device is unplugged, that device or its outlet is very likely part of the loop.
- If unplugging everything except the interface and computer does not remove the hum, the loop may involve the interface's own power supply or the outlet the whole setup shares with the rest of the room's wiring.
Never remove a safety ground to test this
Cutting or lifting the ground pin on a power cable can eliminate hum, and it also removes a real electrical safety protection. Do not do this as a troubleshooting step. Safe fixes exist that do not compromise grounding, covered below.
Fixing It Without Compromising Safety
The safest and most effective fix is usually running everything in your recording chain from a single power strip or outlet, rather than spreading the interface, computer, and any powered monitors across different circuits in the room. A single shared ground path removes the multiple-path problem that causes the loop in the first place, and it costs nothing beyond rearranging cables.
- Consolidate to one power source. Interface, computer, and any powered accessories on the same strip or outlet, rather than scattered across the room's circuits.
- Try a different USB or Thunderbolt port and cable. A ground loop can sometimes route through the data cable connecting your interface to your computer, not just the power cables.
- A ground loop isolator is a legitimate fix of last resort. These are inexpensive, safe (they do not defeat the safety ground) devices designed specifically to break the electrical loop while keeping the audio signal and the ground both intact.
- Check for the obvious culprit last, because it is easy to miss: a dimmer switch, an old charger, or a laptop running on battery versus plugged in can each independently introduce hum, worth testing individually once the bigger structural fixes are ruled out.
↗ Try the tool
Studio Rescue
Free to try: if a session is already recorded and the hum is baked in, Studio Rescue strips it out while leaving the voice untouched, and shows the measured noise floor before and after so you can confirm exactly how much it actually removed.
Open Studio Rescue →Confirming It Is Not Actually Acoustic
Not every low hum is electrical; an HVAC system, a nearby appliance, or a genuinely untreated room's own noise floor can produce something that sounds similar on a casual listen. The diagnostic test above is the reliable way to tell the difference: acoustic noise does not disappear when you unplug a specific device, and electrical hum generally does not change when you leave the room and come back with the mic still recording.
Electrical Problems Have Electrical Fixes
A hum that survives every acoustic fix you try is a strong signal to stop treating the room and start checking the wiring instead. Most ground loop problems resolve with nothing more than consolidating power sources or trying a different cable, no purchase required, and knowing the difference between an acoustic and an electrical problem saves real time compared to guessing at room treatment that was never going to touch it.