How to remove loud hum/buzz from audio track at DVinfo.net

Troy Davis · June 29th, 2010, 08:24 AM

Hello,

I friend of mine recently recorded a event where this loud buzz/hum/frequency feed was overwhelming the voice audio. We are not sure what caused the problem, but wanted to know if the buzz could be removed and the voice audio increased? We have Sony Vegas 8, but didn't know if there was a better tool to do the job? Or maybe there's nothing that can be done.I have attached a snippet of the file as a .wav attachement.
Any help would be greatly appreciated.

Thanks,
Troy

Don Bloom · June 29th, 2010, 09:32 AM

I could be wrong but to my ear it sounds like a big bad electrical transformer was either nearby OR the camera has a really bad preamp.
Anyway, I would start with the Track EQ or Graphic EQ in Vegas. The Track EQ has 4 "buttons" and everything there can be adjusted. Each "button" represents a different frequency so playing around is acceptable and since it's non destructive you won't hurt anything. Set the EQ paly the clip, if you don't like it change it BUT everytime you change something in the track EQ (which of course is in the track header along with "noise gate" and "track compressor" save the new settings (name it and press the disc icon) so if you want to go back to it you can.
If that doesn't work the try the Graphic EQ but I think you'll find the track EQ might just do the job. Of course remember to take smaller bites at the noise since if you go for it all at once you might change the tenor of the voice also you might need the track EQ and the Graphic EQ combined but if the noise is constant you should be able to get most if not all of it out.

Troy Davis · June 29th, 2010, 09:40 AM

Thanks Don. I'm not sure what caused the problem, but the videographer seem to think it was caused by the wireless handheld mic at the reception. Weird... I will give your suggestions and see what happens.

Troy

Jay Massengill · June 29th, 2010, 10:49 AM

The problem is only in the right channel!
In Vegas, right-click the audio event, select Channels and then pick Left Only.
You'll still need to boost the audio, it's very distant (peaking at only -36db), but at least this will completely eliminate the hum and the left channel of audio is fairly clear of problems except for the very low volume.
I'd guess this was the result of using the incorrect connector, perhaps a mono connector into a stereo input jack?

Troy Davis · June 29th, 2010, 10:58 AM

Jay you are the man. That's it! I saw both channels, but the left channel audio was so low I didn't think there was anything there.
I normalized the track and bumped up the audio and all is well. Kudos to both you and Don.

Troy

Andrew Smith · June 30th, 2010, 06:23 AM

There I was thinking that I'd give the noise reduction processing filter a run (in Adobe Audition) and go for some extra bonus points.

My goodness, the right channel is totally obliterated with the hum. Nothing that can be done with it at all. And then there is just barely enough left in the left channel for you to normalise and rescue the job with. You were so incredibly fortunate!

Andrew

Troy Davis · June 30th, 2010, 07:17 AM

Fortunately the videographer always uses a two mics (shotgun and wireless sennheiser) with their XH-A1 xlr. What's strange is that the ceremony was recorded fine and then they thought they disabled the wireless and was only using the shotgun. I will have to see which device they had in the right channel to see where the problem was. Like you said, they were lucky to have enough audio on the left to pull from.

Jay Massengill · June 30th, 2010, 10:35 AM

Based on your latest description, I now remember that a year ago I had a similar incident involving wireless. It was a Shure ULXP4 base station receiver mounted in an inconvenient location. Once the wireless transmitter was turned off, the receiver didn't put out silence from the secondary unbalanced output, but a loud hum identical to your sample. The secondary output was connected with a short cable to my older Zoom H4 running on battery power, so I don't think it was a ground-loop hum. The primary balanced output that always goes to the room's PA system is always clean. When the transmitter was on, the signal to the recorder was also clean.
In my case it caused no problem because I only needed the audio from when the transmitter was turned on for intro comments and then I could discard the rest of the file and use my other recorded tracks for the main presenter.

June 29th, 2010, 09:32 AM	#2
Don Bloom Inner Circle Join Date: Jan 2003 Location: Chicago, IL Posts: 6,609	I could be wrong but to my ear it sounds like a big bad electrical transformer was either nearby OR the camera has a really bad preamp. Anyway, I would start with the Track EQ or Graphic EQ in Vegas. The Track EQ has 4 "buttons" and everything there can be adjusted. Each "button" represents a different frequency so playing around is acceptable and since it's non destructive you won't hurt anything. Set the EQ paly the clip, if you don't like it change it BUT everytime you change something in the track EQ (which of course is in the track header along with "noise gate" and "track compressor" save the new settings (name it and press the disc icon) so if you want to go back to it you can. If that doesn't work the try the Graphic EQ but I think you'll find the track EQ might just do the job. Of course remember to take smaller bites at the noise since if you go for it all at once you might change the tenor of the voice also you might need the track EQ and the Graphic EQ combined but if the noise is constant you should be able to get most if not all of it out. __________________ What do I know? I'm just a video-O-grafer. Don

June 29th, 2010, 09:40 AM	#3
Troy Davis Major Player Join Date: Nov 2005 Location: Raleigh,NC Posts: 263	Thanks Don. I'm not sure what caused the problem, but the videographer seem to think it was caused by the wireless handheld mic at the reception. Weird... I will give your suggestions and see what happens. Troy

June 29th, 2010, 10:49 AM	#4
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	The problem is only in the right channel! In Vegas, right-click the audio event, select Channels and then pick Left Only. You'll still need to boost the audio, it's very distant (peaking at only -36db), but at least this will completely eliminate the hum and the left channel of audio is fairly clear of problems except for the very low volume. I'd guess this was the result of using the incorrect connector, perhaps a mono connector into a stereo input jack?

June 29th, 2010, 10:58 AM	#5
Troy Davis Major Player Join Date: Nov 2005 Location: Raleigh,NC Posts: 263	Jay you are the man. That's it! I saw both channels, but the left channel audio was so low I didn't think there was anything there. I normalized the track and bumped up the audio and all is well. Kudos to both you and Don. Troy

June 30th, 2010, 06:23 AM	#6
Andrew Smith Equal Opportunity Offender Join Date: Feb 2009 Location: Brisbane, Australia Posts: 3,018	There I was thinking that I'd give the noise reduction processing filter a run (in Adobe Audition) and go for some extra bonus points. My goodness, the right channel is totally obliterated with the hum. Nothing that can be done with it at all. And then there is just barely enough left in the left channel for you to normalise and rescue the job with. You were so incredibly fortunate! Andrew

June 30th, 2010, 07:17 AM	#7
Troy Davis Major Player Join Date: Nov 2005 Location: Raleigh,NC Posts: 263	Fortunately the videographer always uses a two mics (shotgun and wireless sennheiser) with their XH-A1 xlr. What's strange is that the ceremony was recorded fine and then they thought they disabled the wireless and was only using the shotgun. I will have to see which device they had in the right channel to see where the problem was. Like you said, they were lucky to have enough audio on the left to pull from.

June 30th, 2010, 10:35 AM	#8
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	Based on your latest description, I now remember that a year ago I had a similar incident involving wireless. It was a Shure ULXP4 base station receiver mounted in an inconvenient location. Once the wireless transmitter was turned off, the receiver didn't put out silence from the secondary unbalanced output, but a loud hum identical to your sample. The secondary output was connected with a short cable to my older Zoom H4 running on battery power, so I don't think it was a ground-loop hum. The primary balanced output that always goes to the room's PA system is always clean. When the transmitter was on, the signal to the recorder was also clean. In my case it caused no problem because I only needed the audio from when the transmitter was turned on for intro comments and then I could discard the rest of the file and use my other recorded tracks for the main presenter.