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Old December 1st, 2005, 07:10 PM   #1
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Fixing audio interference

Hi,

I'm having a problem. I'm working on a documentary, with the interviewee on a wireless lav about 30 - 40 feet from the camera. He sounds great, except in this one particular spot.

[ Download Sample ]
(6 seconds, 378kb wav)

For those who don't have the time or means to listen to it, it's a very high-pitched noise, that kind of sounds like stars flying by you.

I have Adobe Audition, but I'm not sure how to use it in this case. I don't know my audio terminology very well (yet), so does anyone have an idea of what kind of filters would be used to dampen this kind of interference?

Thanks.
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Old December 1st, 2005, 07:46 PM   #2
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Apparently old age is an effective fillter--I can't hear any high pitched tone. I do hear a few surging hisses. Is there a tone present that I can't hear?

If so, I do own SoundSoap, and one of its optional noise reduction approaches for pure voice audio is to filter out everything above and below the voice range. I could run that function on your sound clip and email it back to you if you'd like.
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Old December 1st, 2005, 08:09 PM   #3
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It's not hard to get the out of range shwoosh you have on the track in Audition. NR plus hiss reduction gets it close, but you will need to adjust some eq settings afterwards.

Here (url now removed) is the effect of the 2 aforementioned filters as they affect your supplied track.

Email me your phone number and I can call you ... or you can call me..... 519 8** ... email me for the rest...

Jimmy.

Last edited by Jimmy McKenzie; December 1st, 2005 at 08:59 PM.
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Old December 1st, 2005, 08:21 PM   #4
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Fred,

You're right - there's no tone that you aren't hearing. It's just the hissing that I was referring to.

Jimmy,

Wow - that reduction is pretty incredible! I'm going to try to recreate it myself; partially as a learning experience, and it would also be nice to apply it to a little bit more of the clip.

I'll try it myself, but if you can tell me a little more specifically what you did, that would help. Did you do any keyframing to the hiss reduction filter or was it just one setting?

Thanks. :)
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Old December 1st, 2005, 08:31 PM   #5
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If I was forced to guess, what it seems to me that I am hearing is not the 'out of range' swoosh, but rather the swoosh produced when clothing fabric is in motion around the area of the wireless mic. Perhaps the speaker was moving his arms or shoulders slightly while speaking.

I am probably way off on this, but the few times I have heard the 'out of range' noise, it was significantly more dramatic, but I have heard this tone (the one posted) at various times when speakers wearing lapel mics were moving their clothing slightly.

If this was the case, Douglas Spotted Eagle posted a tip somewhere (I can't remember where or when) regarding what he uses to cover his lapel mic screens (silk maybe) to provide a noise-free sound on the screen when sliding against clothing.
-Jon
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Old December 1st, 2005, 08:50 PM   #6
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I thought so also Jon when I read the initial post. But if you listen again, the shwoosh ramps in less so than a brush with fabric. It also has a degree of off axis noise which would point me toward the logarithmic ramp up of a sennheiser ew100 or 300 eng set going a tad out of range ...

Do tell Allen ... were you using an on camera eng set? The non-diversity variety?
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Old December 2nd, 2005, 11:26 AM   #7
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Quote:
Do tell Allen ... were you using an on camera eng set? The non-diversity variety?
Not quite sure what you mean by that. I completley forget the model of my mic (I'll need to go look it up). It's an azden mic - a relativley cheap one (I think it was the cheapest available). $100-$200 I believe.

It's possible the noise is clothing, but I'm convinced that it's audio interference, still. It's only this dramatic when I'm far away, and he's moving just as much as he normally does. I've also heard the sound before - when I was running this mic through a test, this sound was louder when I got farther away from the transmitter.

I haven't been able to replicate the effects with hiss removal. It helps, but there's still two spikes in the clip that are still present. Audition doesn't have a way to keyframe, does it?
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Old December 2nd, 2005, 12:25 PM   #8
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Click and drag the selected area where you can isolate only the offending noise. Open up the noise reduction window and with about 4000 samples selected click on the get profile button. Hit preview and you will hear the result.

Also, there is a nice tutorial at wrigley http://www.wrigleyvideo.com/videotutorial/index.htm
that shows how to use the spectral view to get out only the noise.

After that the hiss eliminator can be used sparingly.

Then eq the track to bring it back to full where you did the repair.
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Old December 2nd, 2005, 07:07 PM   #9
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Okay, when I use the equilazer, what ranges do I want to push to bring the sound back? The low ranges to try and restore the bass?
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Old December 3rd, 2005, 02:40 PM   #10
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Start with the mids and work your way out...

Keep your finger near the control z button...
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