Sound anomaly at DVinfo.net

Tip McPartland · March 28th, 2007, 10:38 PM

I was doing a shoot the other day, actually just a survey or "recky" as we call it for the real shoot next week, and the audio on my V1U did some very strange things.

I was using aj dual channel wireless and first one channel, then the other got heavy noise -- interference sounding static. Of course I suspected the wireless as they are new to me and unproven. So given the nature of the shoot with quality not too important and speed of the essence, I switched to the on-camera mic. It had the exact same "interference" on both channels.

I quit shooting there and tried again at the next location with the on-camera mic, then everything was perfect. Later at home I tested the wireless and everything worked perfectly. Playback at home confirmed that the noise at the first location was indeed recorded to tape and I couldn't discern a difference between the noise with the wireless and with the on-camera mic.

So it had to be some internal glitch in the camera or some really strange RF thing beyond my experience (eight years of location sound) that would induce noise somewhere in the camera or in all the mics. But for awhile during the first take one channel (one mic?) still worked. Really mysterious.

Tip

Anybody have an idea what this was or a similar experience?

Steven Davis · April 3rd, 2007, 02:00 PM

Brand new cam, I'd be sending Sony a clip of the footage with the caption; Umm, what?

Doug Graham · April 4th, 2007, 08:05 AM

Were you wearing a cell phone at the time? If so, was it by chance one with "walkie talkie" capability?

Steven Davis · April 4th, 2007, 08:24 AM

Quote:

Originally Posted by Doug Graham

Were you wearing a cell phone at the time? If so, was it by chance one with "walkie talkie" capability?

That is an excellent point. I know I've had interference with my wirless mic because people are taking freakin pictures with thier phones.

Douglas Spotted Eagle · April 4th, 2007, 08:40 AM

GSM phones are well-known for their noise/interference challenges to other audio gear.

Steve House · April 4th, 2007, 10:14 AM

As Doug etc said, cell phones and blackberrys "phone home" every few minutes to let the network know what cell they're in, even when the phone is not in use. That's how the system knows which tower to route the call through when someone calls you. All it takes for them to potentially interfere with your audio is for them to be powered on. Insist that everyone one the set completely shut off their devices when you're rolling!

Ralph Keyser · April 4th, 2007, 10:41 AM

I've seen RF interference sweep across a block of wireless units before with each unit going to hash a handful of seconds behind the previous one. We figured out that the order was frequency dependent with the lowest operating frequencies going out first. The mess was gone in about 15 minutes, and we never figured out the source. UFOs? Strange military mind control project? Who knows.

Any airports or military bases close to your location? How about cell phone towers? TV stations? High voltage power lines?

Chris Hurd · April 6th, 2007, 08:06 AM

Quote:

Originally Posted by Douglas Spotted Eagle

GSM phones are well-known for their noise/interference challenges to other audio gear.

As well as ILS, VOR, GPS and other delicate navigation-related systems in commercial aircraft, hence the reasons why their usage is prohibited "until the aircraft is safely on the ground" throughout all US-operating commercial air carriers (some air carriers in other countries are transitioning to RF-shielded cabins).

http://www.spectrum.ieee.org/mar06/3069/3

"In March 2004, acting on a number of reports from general aviation pilots that Samsung SPH-N300 cellphones had caused their GPS receivers to lose satellite lock, NASA issued a technical memorandum that described emissions from this popular phone. It reported that there were emissions in the GPS band capable of causing interference."

March 28th, 2007, 10:38 PM	#1
Tip McPartland Major Player Join Date: Nov 2005 Location: Crestline, California Posts: 351	Sound anomaly I was doing a shoot the other day, actually just a survey or "recky" as we call it for the real shoot next week, and the audio on my V1U did some very strange things. I was using aj dual channel wireless and first one channel, then the other got heavy noise -- interference sounding static. Of course I suspected the wireless as they are new to me and unproven. So given the nature of the shoot with quality not too important and speed of the essence, I switched to the on-camera mic. It had the exact same "interference" on both channels. I quit shooting there and tried again at the next location with the on-camera mic, then everything was perfect. Later at home I tested the wireless and everything worked perfectly. Playback at home confirmed that the noise at the first location was indeed recorded to tape and I couldn't discern a difference between the noise with the wireless and with the on-camera mic. So it had to be some internal glitch in the camera or some really strange RF thing beyond my experience (eight years of location sound) that would induce noise somewhere in the camera or in all the mics. But for awhile during the first take one channel (one mic?) still worked. Really mysterious. Tip Anybody have an idea what this was or a similar experience?

April 3rd, 2007, 02:00 PM	#2
Steven Davis Inner Circle Join Date: Jun 2004 Location: Richmond, VA Posts: 3,065	Brand new cam, I'd be sending Sony a clip of the footage with the caption; Umm, what? __________________ What happens if I push the 'Red' button?

April 4th, 2007, 08:05 AM	#3
Doug Graham Video Bear Join Date: Jan 2002 Location: Stafford, VA, USA Posts: 45	Were you wearing a cell phone at the time? If so, was it by chance one with "walkie talkie" capability? __________________ Regards, Doug Graham

April 4th, 2007, 08:40 AM	#5
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	GSM phones are well-known for their noise/interference challenges to other audio gear. __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

April 4th, 2007, 10:14 AM	#6
Steve House Inner Circle Join Date: Mar 2005 Location: Hamilton, Ontario, Canada Posts: 5,742	As Doug etc said, cell phones and blackberrys "phone home" every few minutes to let the network know what cell they're in, even when the phone is not in use. That's how the system knows which tower to route the call through when someone calls you. All it takes for them to potentially interfere with your audio is for them to be powered on. Insist that everyone one the set completely shut off their devices when you're rolling! __________________ Good news, Cousins! This week's chocolate ration is 15 grams!

April 4th, 2007, 10:41 AM	#7
Ralph Keyser Major Player Join Date: Aug 2002 Location: Albuquerque, New Mexico USA Posts: 287	I've seen RF interference sweep across a block of wireless units before with each unit going to hash a handful of seconds behind the previous one. We figured out that the order was frequency dependent with the lowest operating frequencies going out first. The mess was gone in about 15 minutes, and we never figured out the source. UFOs? Strange military mind control project? Who knows. Any airports or military bases close to your location? How about cell phone towers? TV stations? High voltage power lines?