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Odd Noise on Event Audio Recording

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Max Entman
Odd Noise on Event Audio Recording
on May 23, 2011 at 2:40:07 pm

Hi Folks-

Wondering if anyone can help me diagnose this peculiar buzz present in a couple of our recent audio recordings. It seems to occur every six seconds and pretty much ruins the whole file. We are using Marantz solid state recorders rolling to compact flash cards in MP3 format. They are recording our house feed from wired push-button table top mics.

I've attached a sample of the issue at the link below. Thanks for any of your suggestions!

Best,
Max

Sample of noise issue


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Noah Kadner
Re: Odd Noise on Event Audio Recording
on May 23, 2011 at 3:04:43 pm

I'd guess some sort of EM noise- i.e. some one's phone, wifi router, HVAC, walkie-talkies, nearby radio station, alarm system, etc. I'd guess the cable run was long enough from the feed to the recorder to attract interference or maybe not enough shielded cables. Perhaps even a loose connection. Was no one monitoring the record loop?

Noah

Unlock the secrets of 24p, HD and Final Cut Studio with Call Box Training. Featuring the Panasonic GH2 and Canon 7D.


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Bill Davis
Re: Odd Noise on Event Audio Recording
on May 23, 2011 at 8:25:47 pm

I'd concur with Noah,

The "two pulse" character and the spacing of the pulse groups seems to me typical of a cel phone ring tone pattern.

If you're using balanced audio gear and all the balanced lines are properly functioning, I would expect this to be common mode noise that would be phase-cancelled.

But clearly it's not.

If you cables test good, you need to look at isolating each stage of your audio chain until you can figure out at what point the RF signal is leaking in.

Something fundamental is not working properly.

"Before speaking out ask yourself whether your words are true, whether they are respectful and whether they are needed in our civil discussions."-Justice O'Conner


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Richard Crowley
Re: Odd Noise on Event Audio Recording
on May 23, 2011 at 8:27:59 pm

It is a (quite well-received) repeated digital RF message of some kind. Given the kinds of RF emitters people carry around in their pockets, and the kinds of things found in typical meeting venues these days, it could have been any of a dozen different things. Maybe even a cell phone if it was in some cell service-deprived area. The phone could have been repeatedly searching for service, etc.

Of course, this is why recording audio without CONTINUOUS MONITORING is like framing and focusing your video camera without looking at the viewfinder. If you aren't going to monitor it, why bother even recording it? Especially in a live, location event.


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Max Entman
Re: Odd Noise on Event Audio Recording
on May 23, 2011 at 8:36:28 pm

Thanks so much for the helpful comments. We are a non-profit organization with 3 staff recording 1600 public events a year, so continuous monitoring is not possible unfortunately. This has happened twice in the past year, and we can't replicate the noise. My best guess so far is that there's some kind of loose cable or some electrical device that is turned on at random times in the sound closet.

Best,
Max


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Noah Kadner
Re: Odd Noise on Event Audio Recording
on May 23, 2011 at 11:00:47 pm

Yeah I'd suggest better cables or reduce the distances. Put the recorder right next to the house feed. And if you're non-profit- get some interns. :) As said above- not monitoring audio directly negates the purpose of recording it.

Noah

Unlock the secrets of 24p, HD and Final Cut Studio with Call Box Training. Featuring the Panasonic GH2 and Canon 7D.


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Ty Ford
Re: Odd Noise on Event Audio Recording
on May 24, 2011 at 10:50:44 am

Max welcome to the Cow Audio Forum.

"continuous monitoring is not possible unfortunately"

As mentioned above, adhering to "best practices" makes your position unacceptable. If there was any doubt, you now know why. Someone has to be there to put the machine into record, right? Do they hit record and leave the venue? Of course, in this case, what would they do if they heard the noise?

We live in an increasingly EMF and RF-polluted world. Cell phone, blackberry, and other personal devices are the two edged sword. We like them, but they wreak havoc with our audio, even when balanced mics and cables are used.

There's a saying about doing the same thing over and over and expecting a different outcome. Even if you do try the above suggestions, unless you listen, you'll never know. That's audio roulette. So, every time you fire up, you have to ask, "Do I feel lucky?"

The real point here is, if these recordings are of value to you, do the right thing. The price for doing that is more than you expected. That's the price. It's not negotiable.

Regards,

Ty Ford

Want better production audio?: Ty Ford's Audio Bootcamp Field Guide





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Richard Crowley
Re: Odd Noise on Event Audio Recording
on May 24, 2011 at 2:47:02 pm

If you are a non-profit group, then at least find a volunteer to monitor the audio. You have proved first-hand why it is mandatory.


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