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Old July 16th, 2004, 09:59 AM   #1
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Audio problem- Air Conditioning Noise!

In a wedding rehearsal tonight while testing my audio system (Sony UWP-C1) I immediatly noticed a problem with the audio....the air-conditioning. To the naked ear it's very subtle but in the lav mic it's incredibly loud and roaring. It's got to be something to do with the omni directional pickup pattern of my lav mic- similar to when shooting outdoors a plane flying by far above can sound incredibly loud on tape despite the fact it's fairly quiet in person. What do I do in this situation? Is a noise reduction plug-in my only hope?
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Old July 16th, 2004, 10:02 AM   #2
 
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CAn't get a uni in there? If not, you're stuck with post-repair.
But...get as much signal to noise as you can, and most of the time, the Noise Redux will work great.
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Old July 16th, 2004, 10:55 AM   #3
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CAn't get a uni in there? If not, you're stuck with post-repair.

Problem is I kind of need the non-directional pick up of an omni to gather audio from the Priest and Bride, in addition to the groom.
Won't a Uni hinder this ability?



But...get as much signal to noise as you can, and most of the time, the Noise Redux will work great.

By that do you mean try to get the source audio to be as loud as possible. If so I completly understand I've tried cleaning audio where the source audio and "noise" were very similar in db...it was impossible to do a good job of cleaning it up. Here's hoping that the couple doesn't whisper their vows.
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Old July 16th, 2004, 11:10 AM   #4
 
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If close in, less than 24 inches or so, you should be able to get fine audio with a uni. Can you run both, and use the uni on the left channel, and omni on right channel of your cam?

By good signal to noise, I mean a good dynamic, so that the noise is lesser than the voice. Usually, air conditioner noise is quite easy to clear. Not always though.
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Old July 16th, 2004, 11:19 AM   #5
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I've had great success in cancelling noise from fans and AC by using the Noise Reduction filter in Adobe Audition. The trick is to make sure you have a good audio clip of the AC running without anything else going on.
http://www.wrigleyvideo.com/videotut...tion_noise.htm

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Old July 16th, 2004, 02:20 PM   #6
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<<<-- Originally posted by Douglas Spotted Eagle : If close in, less than 24 inches or so, you should be able to get fine audio with a uni. Can you run both, and use the uni on the left channel, and omni on right channel of your cam?

By good signal to noise, I mean a good dynamic, so that the noise is lesser than the voice. Usually, air conditioner noise is quite easy to clear. Not always though. -->>>



Well I usually try and place the lav mic a bit low on the grooms jacket that way it makes the audio device more equadistant between the bride and grooms head. If it were placed high- up near collar area it would definitly be closer to the groom than bride and give much stronger audio from the groom. However in this situation due to the noise level I might have to do just that to get stronger audio.

Regarding having the uni and omi running simultaneously- that's what I'm already doing. Using my on-camera ME66 shotgun on channel 1, and the UWP-C1 wireless on channel 2. In post I duplicate the audio track, right click and choose "left only" for one, and "right only" for the other (in Vegas...naturally). That way I have a complete track from both sources- no stereo imaging lost beings both original sources were mono to begin with.

I'm going to have to get up and running with noise reduction. I must admit I don't always get good results with it- though it could be due to my source audio. I generally look for the cleanest noise print...and run several passes with very conservative settings rather than one pass with drastic settings.
The point you made about having the vocals be much louder than the noise is quite true. If anything it's one of the biggest deciding factors in how sucessfull you can be using noise reduction.

Problem is from the short tests I did last night the subjects will have to speak quite loudly to overcome the air conditioner noise and couples tend to speak softly when repeating vows. *wish me luck* I'll post my results if you guys would like.
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Old July 16th, 2004, 02:30 PM   #7
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See if they won't shut down the AC for the 10 minutes that the actual ceremony is taking place.
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Old July 16th, 2004, 02:34 PM   #8
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Make _sure_ you get in there early and record a minute or
two of "silence". That way sampling the noise will be easy
for a program like sound soap or waves X-noise.

You may find that putting that silence out of phase and mixing
it in the with 'good' audio will result in noise reduction via phase
cancellation. It is much easier to do this if you have several
minutes of the offensive noise floor with which to work.

Spot is right. Having lots of signal (loud voices) with which to work
is best, but also risky in red lining your recording.
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Old July 16th, 2004, 03:14 PM   #9
 
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http://www.sundancemediagroup.com/help/kb/kb_tutorials.asp

Read "The Art of Noise", which should come up first in the list, depending on how you have your thread views.
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Old July 16th, 2004, 09:24 PM   #10
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I didnt take the time to read the other posts,......but. If you have audition, the noise reduction is great, only if you use the spectral decay. Start at 20-30% and work your way up to as much as 65-70%. It helps get rid of the "fake" sound that goes hand in hand with to much noise reduction.

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Old July 16th, 2004, 09:30 PM   #11
 
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All I can say is...if you guys are impressed with Audition's noise reduction, you GOTTA try Sony's. Ask anyone who has seen me demo it. (and I tech edited the book on Audition, it's a FINE product. But for sub 2.5K, Sony's is unbeatable)
SoundSoap PRO, not the 99.00 tool is exceptional too, and of course, WAVES X-Noise is very good too. All three better than Audition's by a landslide. But, if you're happy with the lower cost tool....
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Old July 17th, 2004, 11:17 PM   #12
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Hey, I hope I'm not too late for the wedding. To make the post processing job easier, stick to manual gain (not AGC). If you're not moving the camera around, the hum part of the AC noise will be constant, and the phase inversion trick mentioned earlier will work on the hum part. Try it, although the recording will have to be uninterrupted for that trick to work.

I've used noise reduction on SoundForge, and it does anreasonable job of 20 dB attenuation if the noise fingerprint actually matches the noise. However, this often results in a somewhat robotic quality of the final audio, at least for the audio I've tried to rescue this way.

If the advanced noise reduction doesn't do it for you, do a spectral analysis of the isolated A/C noise and add narrow notch filters for the prominent hum frequencies. Then, add a Noise Gate function.

Also, have you considered turning off the AC for the ceremony,
which is usually quite short? At the very least, you could shut it off for the vows.

Good luck,

Gints
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Old July 18th, 2004, 12:29 AM   #13
 
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<<<-- Originally posted by Gints Klimanis :

I've used noise reduction on SoundForge, and it does anreasonable job of 20 dB attenuation if the noise fingerprint actually matches the noise. However, this often results in a somewhat robotic quality of the final audio, at least for the audio I've tried to rescue this way.
-->>>
Gints, in *most* cases, if you are only getting 20dB out of Sony Noise redux, you're grabbing way too large a slice of noise. If the signal and noise are similar in range, and similar in level, then 20dB might be all you'd get...but that's pretty rare when you know what you're doing, and I'm sure you're getting better signal to noise. Try grabbing the smallest possible slice of noise you can grab. You'll do better.
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Old July 18th, 2004, 10:40 AM   #14
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Gints: "To make the post processing job easier, stick to manual gain (not AGC).

Oh I ALWAYS use manual gain- turning off AGC was one of the first things I did when I got the camera- that and turn the audio khz from 32 to 48.

"Also, have you considered turning off the AC for the ceremony,
which is usually quite short?


lol...not Catholic Ceremonies- in addition to the wedding they had practically a full mass- was over an hour. The two remote cams (one in balcony, one on floor behind last pew) ran out of slack before the recessional. Thus I didn't get the couple walking the isle together. I had to other manned cameras though (btw this was my first shot at a 4-camera shoot).







Spot: "Try grabbing the smallest possible slice of noise you can grab. You'll do better."

Is this always a rule- I remember seeing this technique in your Class on Demand DVDs but never thought to ask about it.

Btw, the wedding is done- the air conditioner ran the entire time. I do, however, think the audio turned out much better than I had expected. I haven't had a chance to capture it, separate the channels, and review it- but will do so quite soon. On a different not this was the first wedding I shot using wireless audio aquisition for the vows- I know I'm behind the times! With the groom wired it was entertaining to say the LEAST hearing the little conversations the bride and groom had during the middle of the ceremony.

Thanks for your input everyone!
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Old July 18th, 2004, 11:24 AM   #15
 
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Always grab the smallest slice, and then if you need to run Noise Redux more than once, do so. When we did the Smithsonian work, I ended up processing some files as many as 10 or so times.
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