Removing mic hum/buzz

Hi, I have Audacity 2.0.5 in Windows 7. I need help. Apparently I did not ground my mic properly, or something like that, and have a horrible hum/buzz running through the audio portion of my videos. I have tried several things to fix this - Noise Removal, Nyquist Prompts and Notch Filters in Audacity and Audio Restoration and other FX in Sony Movie Studio but I still don’t have good sound quality during speaking parts. I’m a novice and I know I don’t have the settings right. I’ve watched several YouTube videos and get how to work Noise Removal but probably don’t have the settings correct there either. The hum is removed when people aren’t talking but is still in the background when they are and their voices are a little distorted and “pumping.” Can anyone help? I hope so! Thanks!!

If you post a short sample (just 3 or 4 seconds) of the original unprocessed audio (WAV format please) then we can have a look to see what can be done.
See here for how to post an audio sample to the forum.

I will post a sample now. It’s awful.

Here’s 6 second untouched sample. First part is just the noise and then there’s a bit of dialog. Thanks for anything you can do!!

Didn’t look like file was attached to last comment so trying again. It keeps saying the file is too big. I think this is only 4 seconds.

Yes, that does sound like an open microphone ground or bad or dirty connection. Alcohol or vodka and a clean rag are your friend.

Someone posted a power line hum and buzz rejector that might help, but you should get used to the idea of a reshoot. Hum that bad takes over the AGC in the camera and makes sure that the majority of the show is hum. In order for most of the repair tools to work, the show has to be a lot louder than the hum.

In other words, we can’t do “CSI” forensics.


I got pieces of this:


You probably can’t eliminate the hum completely, but it can be substantially reduced.

First, run this code in the Nyquist Prompt effect:

(do ((i 1 (+ 2 i)))
    ((>= (* i 60) (/ *sound-srate* 3)) s)
  (setf s (notch2 s (* 60.0 i) (* 8.0 i))))

Then with the Noise Removal effect, capture a noise profile from the remaining buzz,
then apply Noise Removal with these settings:
Here is before/after:

Wow!! Your version sounds much better than anything I tried to do! Thank you so much! I’ll try it now following your instructions. I downloaded a trial version of Sony Sound Forge to listen to it but do I need it to make the improvements? I love Sony Movie Studio and plan to upgrade to Sony Vegas at some point but didn’t want to have to purchase Sound Forge at this time. Thank you so much! Going to try it now. I know it’s best to redo it but I really can because I filmed it for a client in Ohio and I"m in MI and on deadline and people were brought in from around the state, etc. It mic worked fine before I plugged the camera into a power strip that I used as an extension cord. Guess that was my first mistake!

Steve - thank you so, so, much!! You saved the day! I’ve never posted on a forum and have always just tried to find similar situations. I wish I would have posted this morning because I spent last night and all morning trying to figure this out and obviously I’m very much a newbie. Thank you, thank you, thank you!!! I actually have several clips to adjust but they were all shot in sequence with the same set-up so I’m sure your coding and settings will work on all of them. Thank you again! :smiley: :smiley:

I doubt that SoundForge could remove the buzz as effectively as this.
Writing Nyquist scripts is not everyone’s cup of tea, but it is an extremely powerful tool for accomplishing special one-off jobs like this. I’m sure there is a Nyquist plug-in already written for buzz removal (probably in the “New plug-ins” section of this forum), but it was quicker for me to just write the script rather than hunting down the plug-in.

If all you did was stop and start the camera, then yes, chances are good that all the clips may take the same settings.

The Big Kids listen to a sample of the performance recording before everybody goes home. If possible, listen to a snippet just before the take. You should be listening to the camera during the show, too. That would have certainly been damaged. That’s what’s going on with those shoots where at least one person is wearing large headphones.

A video shoot without the video is called radio. A video shoot without the sound is called trash (or a rehearsal).


I appreciate everyone’s help and feedback. I knew I would open myself up to some “advice” by posting but as I said, I’m fairly new to video production, self-taught, and have learned a few things the hard way. My first thought was I should have had on headphones. I checked the sound after the first couple segments and then figured it was fine even though I switched rooms and plugged it in. Bad assumption. I did realize the buzzing before people left but didn’t have the heart to ask them, or the time, to do it over. I’m so thankful Steve wrote that code for me. That’s something I couldn’t have done in a million years! Thanks so much again!!

Whoops, guess it’s not even called code. Scripts! Thanks for writing the scripts Steve. I appreciate it so much!

“script” / “code” / whatever, the distinction between one and the other is not really important. Traditionally “interpreted languages” have been referred to as “scripts”.
As for “a million years”, probably more like a couple of weeks to be able to write your own filter scripts if you did a bit of reading and experimenting :wink:

The script that I just posted is a bit more complex than many because it loops round lots of times to notch out the 60 Hz buzz, and then each odd harmonic (180 Hz, 300 Hz, 420 Hz …) up to about 16000 Hz. The basic filter each time is in the form (notch2 s frequency q) where “notch2” is a filter that removes a narrow band of frequencies, “s” is the selected audio, “frequency” is the centre of the band to remove and “q” is the width of the frequency band (higher number for a narrower notch). :nerd:

Very impressive if you ask me! Maybe I could learn it but these videos are due in two weeks. I PM’d you because I’m wondering what’s the best way to replace the old with the new in Sony Vegas/Movie Studio. I have several clips to fix and I know how to do it on the timeline but don’t see how to create a new mp4 file without rendering which would take forever. I thought I saw someone on YouTube do it in one step during the Export.

I did realize the buzzing before people left but didn’t have the heart to ask them

You know the standard picture everybody has of a film shoot where the director yells “Roll!” and the camera operator yells “Rolling!” and the director yells “Action?” There’s a step missing. The Sound Guy in the back of the room yells “SPEED!” and then the director yells “Action.”

Actually, there’s more steps in the middle, but those are the important ones.

That’s a little less of a problem with cameras that record sound with the picture, but if you’re on a classic separate sound shoot, all four people have to be holding hands. On any shoot, the sound recordist has the important job.


My dream is to have all those people working with me. Right now I’m a one-person show and my lack of technical skills with a camera, sound, etc. are very frustrating at times. I love the production side of it.