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Old August 20th, 2012, 09:15 AM   #1
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Looking for a good lavalier mic that is impervious to GSM / cell phone interference

I have some Audio Technica AT803B microphones that do a great job, but they are very susceptible to the "GSM buzz" or cell phone noise. (If you're not familiar with the noise, check out Cellular Signal Noise)

Anyway, I'm looking for a similar mic that would NOT pick up the noise. I think this must be possible because I have shotgun mics that don't pick it up, and I also have wireless sets that don't pick it up. So I would assume there's a similar mic that doesn't pick up the noise.

Any thoughts?
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Old August 20th, 2012, 09:31 AM   #2
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

At what distance? Using what other equipment?

If you are looking for something that is impervious to a cell phone in another pocket of the user (the wearer of the lav mic) then you are dreaming. The RF field is so great at short distances that NOTHING is really "impervious". Certainly not baseband audio equipment, and especially not high-impedance, very low-level devices like electret microphones. The ONLY cure for this situation is to turn off or remove the phone from the user.

Note further that SOME of the vulnerability is in the wiring and/or connectors, and particularly in the input circuit of the terminating equipment (i.e. the wireless transmitter or the XLR adapter, etc.) You can do some limited "RF hardening" to some equipment.

But there is almost nothing worse than a pulse-mode GSM cell phone, especially one searching for a cell connection. They put out a stream of RF pulses that resembles the kind of jamming that was commonplace during the cold war in the repressive communist totalitarian regimes of eastern Europe.
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Old August 20th, 2012, 10:37 AM   #3
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

The most common scenario is in a conference room, with people having lavalier mics clipped on. Oftentimes, they will have their cell phone either in their pocket or resting on the table in front of them.

Maybe it's not possible to get rid of 100% of all of the interference, but it seems like some mics do a much better job than others. For instance, we have some Lectrosonic wireless pairs (not sure the model) that don't seem to ever pick up any type of cell phone noise.

Since I posted this, I've been doing more research, and I might be even answering my own question. It seems Shure has a microphone, the MX150, which is supposed to have some form of EMI / RF guard or shielding. I also was reading about Audio Technica and their "UniGuard" shielding, which seems to be essentially the same thing.
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Old August 20th, 2012, 12:57 PM   #4
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

Black Berry and other extraneous rapid beeping type noise are often induced though a mic cable. Try replacing the cable with a star-quad design, from Canare, Belden or Mogami. before spending $3k on a Lectro system.,.. though a Lectro is a good gear investment
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Old August 20th, 2012, 03:32 PM   #5
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

Thanks for the suggestion, Rick. Could you give me some info on where I could find one of those star-quad designs you're talking about? I don't think I've ever heard of them.

The Lectros do work well, but I'd rather not have wireless mics, mostly due to having to swap out the 9V batteries every now and then.
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Old August 20th, 2012, 03:45 PM   #6
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

I should add that it appears the interference/noise is coming in on the thin wire between the actual microphone itself and the power pack. Everything seems okay from the XLR cable on, so it seems the vulnerability is with that thin microphone cable.
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Old August 20th, 2012, 05:23 PM   #7
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

Typically a lav is unbalanced so it's not surprising the the culprit woulds be the cable between the mic capsule itself and the power supply/balancing transformer/XLR adapter.
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Old August 20th, 2012, 09:46 PM   #8
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

With that in mind, I wonder if there's anything I can do to mitigate the damage or lessen the intensity.
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Old August 21st, 2012, 04:48 AM   #9
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

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Originally Posted by Luke Arndt View Post
With that in mind, I wonder if there's anything I can do to mitigate the damage or lessen the intensity.
Yes - insist all mobile phones are switched off or set to "Airplane Mode" while you are recording.

This is standard in all professional recording situations.
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Old August 21st, 2012, 07:03 AM   #10
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

Right... I already ask them to do that.

The problem is, these are depositions in conference rooms, so it's not your standard professional recording studio/set. People fall into old habits, or they just don't comply thinking that it's not really necessary to have the radios fully off.

With that in mind, I'm trying to find a way around that. And like I mentioned, some microphones DO seem to deal with it much better than others, so it's just a matter of finding the right equipment/retrofitting my own to work better.
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Old August 21st, 2012, 08:14 AM   #11
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

If you are doing depositions...
A) Do everybody a favor and skip the wireless mics. They are more trouble than benefit in this scenario.
B) Leave it up to the attorneys how serious they are about having interference-free recordings.
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Old August 21st, 2012, 08:56 AM   #12
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

I know wireless has its advantages, but I was also kind of hesitating to use them. Here are the cons, as I see them:

* Possible static/interference over the air
* Having to swap out/charge batteries
* The risk of somebody forgetting to take it off when leaving the room

The benefits, on the other hand:

* What seems to be better resistance to cell phone interference
* Tidier. Not having to string cables all over the place.

Anything else that I'm missing?
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Old August 21st, 2012, 11:41 AM   #13
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

NEVER EVER use wireless when you can use a wired microphone! Depositions are a perfect example.

A solid-gold $10,000 wireless microphone can NEVER EVER be as good as an ordinary $20 cable! In any and every situation.

A wireless microphone is ALWAYS a 2nd choice compromise over using a wired microphone.

Wireless microphones are MUCH MUCH *MORE* susceptible to cell-phone interference. I have thousands of dollars worth of wireless mics that have been rendered useless in places where cell phones cannot be controlled.

I would NEVER bring a wireless microphone to a deposition shoot.
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Old August 21st, 2012, 10:03 PM   #14
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

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Originally Posted by Richard Crowley View Post
I would NEVER bring a wireless microphone to a deposition shoot.
There is a reason broadcast mixers go hardwired most of the time. Unless mobility is a necessity...wire works!

Let me add, a balanced mic into a balanced input on a recorder will be your best defense against RFI.
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Old August 22nd, 2012, 12:12 AM   #15
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Re: Looking for a good lavalier mic that is impervious to GSM / cell phone interferen

XLR is always balanced... right? I go XLR from the mic to the mixer, then XLR from mixer to recorder (camera).

If that's true, then how would I go about finding a balanced microphone itself? Are there certain specs I can look for?

Also, aside from forcing people to actually shut their phones off, have you guys found any tricks at all to minimize the problem? In my experience, it seems like some mics handle it better than others, so I guess I'm wondering if anybody has any recommendations on actual mics or anything I can do to with my existing equipment.

Thanks for chiming in!
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