Need help removing hum at DVinfo.net

Go Back   DV Info Net > The Tools of DV and HD Production > All Things Audio

All Things Audio
Everything Audio, from acquisition to postproduction.


Reply
 
Thread Tools Search this Thread
Old October 1st, 2014, 04:04 PM   #1
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Need help removing hum

Hi,

I have a piece of audio that has a hum or whatever this is called and I don't know how to remove it. I do have Izotope RX but can't figure out how to get rid of it. I am attaching a clip. If someone could tell me what exactly that sound is called and how to best remove it that would be awesome. If you have tips on how to remove it using Izotope RX that would be even better.
https://www.dropbox.com/s/7tjvmom6zwbdphi/Tom.aiff?dl=0
Kathy Smith is offline   Reply With Quote
Old October 1st, 2014, 04:47 PM   #2
Regular Crew
 
Join Date: Jul 2014
Location: Johannesburg
Posts: 44
Re: Need help removing hum

Kathy could it be your audio playback hardware? The audio clip sounds clean to me, I'm either going deaf or there isn't any hum?
Alex Harper is offline   Reply With Quote
Old October 1st, 2014, 04:49 PM   #3
Trustee
 
Join Date: Aug 2008
Location: New York
Posts: 1,844
Re: Need help removing hum

Same here. Clean
"I'm either going deaf or there isn't any hum?"
Same here as well, I even ran it though a analyzer to check.
Rick Reineke is offline   Reply With Quote
Old October 1st, 2014, 05:03 PM   #4
Trustee
 
Join Date: Aug 2007
Location: Portland, Oregon
Posts: 1,177
Re: Need help removing hum

I hear a tiny bit of hum right at the very end when the subject finally takes a breath(!) But it seems VERY far down from the average signal levels. And it seems more like environmental buzz (like from a fluorescent lamp ballast or something) than a traditional mains power hum.

I wonder if we are hearing the same thing? With such a very short snippet, it isn't all that easy to judge, but it seems like it is so much lower than the dialog, it isn't worth bothering with. Perhaps a better sample would illustrate what your think the issue is?

If you are trying to eliminate a "buzz" (vs a "hum") then you must also go after the harmonics up the spectrum. For example Adobe Audition has a filter for 60/120 Hz and another for 50/100 Hz which include notches for at least half a dozen octave-spaced overtones above the fundamental.
Richard Crowley is offline   Reply With Quote
Old October 1st, 2014, 05:36 PM   #5
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Need help removing hum

Yes. It's that buzz sound I'm referring to. It sounds like fluorwscent bulb as Richard said.
If this is not worth rwmoving then I'll leave it as is.
Now next question. How do I make this sound better?
Kathy Smith is offline   Reply With Quote
Old October 1st, 2014, 05:48 PM   #6
Trustee
 
Join Date: Aug 2007
Location: Portland, Oregon
Posts: 1,177
Re: Need help removing hum

I don't have a good playback system available at the moment, but, to my ear, the three things that could be troubling are:

1) It sounds slightly over-driven. Dunno where along the audio chain that happened, and there isn't much you can do about it within a reasonable cost/benefit ratio. I would think it is the kind of thing that could be easily avoided if monitored properly during recording.

2) It sounds somewhat compressed. Perhaps a first-cousin of #1 above. Again, not so bad it would be worth taking extraordinary measures.

3) It sounds just a bit reverberant. But, without seeing the video and knowing what the expectations of the producers are, very possibly well within the limits of perfectly acceptable. There are new software tools becoming available to significantly reduce reverberation, but they seem fiddly and extremely expensive and limited only to acute cases until the cost descends to where most of us live and work.

4) It sounds a bit "tubby" (mid-low frequency bump) But that could very well be attributed to the crummy headphones I have at the moment. Tonal balanced is something that would be pretty easy to apply, and to listen to the results and "season to taste".
Richard Crowley is offline   Reply With Quote
Old October 1st, 2014, 07:57 PM   #7
Trustee
 
Join Date: Jul 2003
Location: Burlington
Posts: 1,961
Re: Need help removing hum

I've listened to the clip on my home computer which has a pretty good set of JBL consumer speakers.

If you thought it was bad enough to come to the forum, then I'd have to ask like Alex, could it be something in your own playback system?

I don't detect anything out of the ordinary beyond the minor characteristics that have already been mentioned.

I'm guessing this was recorded with a lavalier mic?
Jay Massengill is offline   Reply With Quote
Old October 1st, 2014, 08:52 PM   #8
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Need help removing hum

yes, lav mic. Well, I don't think it's bad but I am becoming anal about sound so I thought professionals would want to remove that buzzing sound.
by over-driven do you mean clipped?
Kathy Smith is offline   Reply With Quote
Old October 1st, 2014, 09:36 PM   #9
Trustee
 
Join Date: Aug 2007
Location: Portland, Oregon
Posts: 1,177
Re: Need help removing hum

No, if it were clipped you would know it without asking.

Without knowing anything about your audio path, we can't offer any speculation about WHERE it might have happened. But it was in some linear/analog circuit BEFORE it got digitized into ones and zeros. It might even have been the microphone itself.

We also don't know if/how the audio was monitored, so we don't have any forensic evidence of what happened during recording.
Richard Crowley is offline   Reply With Quote
Old October 1st, 2014, 10:09 PM   #10
Trustee
 
Join Date: Jul 2003
Location: Burlington
Posts: 1,961
Re: Need help removing hum

Can you list the complete audio path during the recording?

And any settings like compressors or limiters used in editing?

It looks and sounds to me like it ran up against a hard limiter at some point. Perhaps an all or nothing limiter switch on a mixer or the camera/recorder.

If that is what happened, then it's possible to keep pushing up the signal feeding into the limiter and it won't allow any more peak signal through, you're just pushing up the background noise and compressing the overall voice. Making it sound a little strident and over-driven but without hitting any point that actually clipped.
Jay Massengill is offline   Reply With Quote
Old October 2nd, 2014, 03:54 AM   #11
Inner Circle
 
Join Date: Feb 2009
Location: Brisbane, Australia
Posts: 2,261
Re: Need help removing hum

I've got studio reference monitor speakers and it sounds great. No hum at all and a very clean recording.

I removed the slight echo in the sample recording. Because I could. :-)

Grab the updated audio from here: https://www.dropbox.com/s/q6hwkqo90t...0echo.aif?dl=0

Andrew

PS. There is a tiny bit of hum / consistent looking noise that you can see on a spectral view of the audio, but it's waay down at the -56db level. Not worth worrying about.
Andrew Smith is offline   Reply With Quote
Old October 2nd, 2014, 08:36 AM   #12
Trustee
 
Join Date: Jan 2011
Location: Pennsylvania
Posts: 1,359
Re: Need help removing hum

Interesting noise. It's not a pure single-frequency hum, nor is it typical power line "buzz" with harmonics every 60 Hz. It is predominantly 120 Hz, 360 Hz, and a small bit at 960 Hz.

Peak level of the noise is about -48 dB. Peak level of the voice is about -4 dB. That makes the S/N ratio -44 dB, which is audible at high normal listening levels (confirmed by my ears).

Looking at a spectral view of the clip, the noise is also present in the small pause around 3.4 to 3.7 seconds, but you don't much notice it there because it's masked by the breath and other ambient noise.

As many have said, no way to guess where it originated, without knowing a lot more. However, it is very easy to remove using the noise sample process in Cool Edit or Audition. Since the level is so low to begin with, it takes very little removal to eliminate it entirely, without any audible artifacts.
Greg Miller is offline   Reply With Quote
Old October 2nd, 2014, 10:18 PM   #13
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Need help removing hum

Thanks for the responses.
The mic was connected to the camera using XLR cable. I am using this EMP4S: Ambient Recording GmbH adapter in order to connect the mic using XLR cable.
Kathy Smith is offline   Reply With Quote
Old October 3rd, 2014, 12:35 AM   #14
Trustee
 
Join Date: Aug 2007
Location: Portland, Oregon
Posts: 1,177
Re: Need help removing hum

I would put that adapter pretty low on the list of suspects.
Exactly what microphone? What camera?
Where was the microphone placed?
Was the subject's speaking voice louder than average?
It would be almost impossible to reveal TOO MANY details here.
Richard Crowley is offline   Reply With Quote
Old October 3rd, 2014, 05:30 AM   #15
Major Player
 
Join Date: Oct 2010
Location: NY, NY USA
Posts: 466
Re: Need help removing hum

Quote:
Originally Posted by Richard Crowley View Post
I would put that adapter pretty low on the list of suspects.
Exactly what microphone? What camera?
Where was the microphone placed?
Was the subject's speaking voice louder than average?
It would be almost impossible to reveal TOO MANY details here.
Microphone: Sanken COS-11D
Camera: Canon C100
Mic was clipped to his jacket on a right side, around 3-4inches down from his chin
I don't recall him speaking louder than average
I had peak limiter on.
Kathy Smith is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > The Tools of DV and HD Production > All Things Audio

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 07:39 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network