Remove Ground Loop Noise


There’s a horrible buzz/hum (seems like ground loop) through most of a recording I’ve received to edit for a friend. I’ve tried noise removal but it seems the only noise that remains is this ground loop sound. I’ve also tried high & low pass filters and equalizing but nothing seems to help. Can this horrible sound be removed?

Noise Removal is something of a violin. It’s not a push the button and everything is fine. It’s find some rosin and tune each string carefully.

The first step in noise removal is to find a portion of the show with noise and no performance. That’s needed for the profile step. That tells Audacity what to remove. If you catch some of the voice or music in there by accident, Audacity will try to remove the voice or music, too.

If the noise is so bad you can’t tell where to get the profile sample from, that’s the end of the story. Noise Removal will not work without that.

Remember when you were manually messing with filters? All Noise Removal is doing is making the filters for you with that profile step.


You could have two problems: A good Open Shield or Ground Loop hum is deadly because it contains tones that go right through the middle of vocal tone range. It’s direct competition. If Noise Removal filters them out and the voice happened to hit one of those tones, you lose. For example, one of the tones in that buzz (in the US) is 300Hz. D above middle C on the piano is 293Hz.

The other thing that can happen if the noise is bad enough it can actually damage the MicPre or Sound Mixer. I don’t mean smoke and fire (although if it’s bad enough…), I mean any loud overload will take out the show. It will not be recoverable.

So yes, the short answer is there’s no show.

This is why the sound guy is hunched over the mixing desk with headphones during the show.


I can make this worse.

If the picture fails you have a nice radio show. If the sound fails, you have a nice excuse for a reshoot.