Interference on audio from mobile phones

Grandad Ron

Member Joined: Sep 17, 2009 04:36 Messages: 66 Offline

Solved by

Jul 25, 2013 05:52

Shooting a school play on the Panasonic 900 and using a Rode Shotgun Mic, positioned on a separate tripod with a short screened extension lead into the mic socket of the camera.

Generally the pick-up from the stage was excellent and the background, whisper quiet, but on two or three occasions the audio picked up short bursts of interference which have been confirmed as coming from a mobile phone, most likely a SmartPhone owned by one of the audience sitting near the camera. I could hear it in the earphones as I was recording, it sounded rather like an angry mosquito and could be clearly heard during the dialogue.

The audience had been asked to switch mobile phones off, so I have to assume that someone. did not switch off, and merely switched to mute ?

I can't find any reference to this situation in the Forum 'search'. Is there anyway to defeat or at least curb the interference without killing the dialogue.

Looking forward to the next shoot, is there a way of making the 'screened' extension lead more secure ?

Grandad Ron

Raputtak

Member Joined: May 26, 2012 22:12 Messages: 51 Offline

Jul 25, 2013 09:30

I am wondering if an RF choke on the mic cord, just before the camera, would do the trick. (An RF choke is that cylinder thingie one finds on some USB cords). One would have to be a dab had at soldering and fabricate a cord - or very adept at using a search engine. Custom computer: 8 processors, 16G Ram, ,C: drive 250G solid state. F: (Scratch drive) 2x 500Gb raid (0). G: (Data drive) 2Tb raid (1)
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borgus1

Senior Contributor Joined: Feb 27, 2013 00:33 Messages: 1318 Offline

Jul 25, 2013 10:00

Quote: I am wondering if an RF choke on the mic cord, just before the camera, would do the trick.

Assorted chokes that fit onto cords, or through which cords are wrapped, are available in the states at Radio Shack.

Carl312

Senior Contributor Location: Texas, USA Joined: Mar 16, 2010 20:11 Messages: 9090 Offline

Jul 25, 2013 10:02

Raputtak's suggestion is a good one for the RF choke.

you do not have to do any soldering. There are RF chokes that clip on the wire.

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GUEA_enUS530US530&q=Ferrite+Core++Noise+Suppressor

Another thing you should check. Make sure the shield of the microphone cable is a good connection.

Wireless microphones do not need wire to connect to the camera and they operate over long distance.
Only the microphone receiver connects to the camera.

Unless the Cell phone is on the same channel (not possible) wireless mics operate on a different band.
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Grandad Ron

Member Joined: Sep 17, 2009 04:36 Messages: 66 Offline

Jul 25, 2013 15:05

Thanks Guys,

The gadget you refer to is something I will attach on my next shoot (on other sites I see it referred to as a ferrite core).

I have those gadgets on a number of my USB cables so it must be useful for something.

Luckily I have managed to edit out the 'NOISY' sections by using footage from the other shoot.

Next year we plan to ensure that the audience check their hardware into the Sheriffs office before the start of the performance, conversely we could hold up the production to name and shame the culprit.

Grandad Ron