Lav mic interference/malfunction

modus

modus

Well-known member
Please watch this 7-second clip. Does anyone know what this audio anomaly comes from? Is there anything I can do to prevent it?

http://www.vimeo.com/12947102

I am using a Sennheiser Evolution Wireless g2 100 wireless kit. I adjusted both the transmitter and receiver to a free frequency before the show. I was probably about 40 or 50 feet away from the groom (maybe closer). The in-house audio guy was on a completely different frequency as well.

Any suggestions would be appreciated.
 
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According to Vimeo, the video won't start converting until around 8:00AM PT. Presumably it won't take very long to convert if it is only 7 seconds long.
 
Apparently it took 30 minutes to convert. I think they do this to annoy you into buying a "Plus"account.

Anyway, it should be working now. Thanks for looking.
 
I'd be interested in the answer... I've run into the same problem, and I suspect it is related to either cellphone or bluetooth interference.

I was getting hits like this on an interior shoot, so I made sure that all cellphones were turned off, as well as the wireless routers & phones. I forgot to check for bluetooth devices & one of the actors had his in his pocket. The hits went away when he left for the day!

I also suspect that even when cellphones are off they still emit "seek" hits for local towers... Maybe the only way to make sure is to have cellphones & bluetooths banned from the location (left in cars) or have the batteries removed. The problem with this is that people have become to addicted to their phones that it becomes a nightmare to enforce.

Oh, yeah- "airplane mode" doesn't mean off!
 
modus said:
Please watch this 7-second clip. Does anyone know what this audio anomaly comes from? Is there anything I can do to prevent it?

http://www.vimeo.com/12947102

I am using a Sennheiser Evolution Wireless g2 100 wireless kit. I adjusted both the transmitter and receiver to a free frequency before the show. I was probably about 40 or 50 feet away from the groom (maybe closer). The in-house audio guy was on a completely different frequency as well.

Any suggestions would be appreciated.
Click to expand...

Yep. Been there. That's exactly what I heard once with my G3. It was discussed in this thread over on DVInfo. The consensus (if you can have consensus on something like this) is crappy cell phone handsets leaking RF all over the place. It's not constant because it only happens when they send/receive packets to/from the local cell tower.

The reason you didn't find it during set up is that the guest with the crappy cell phone hadn't arrived yet.

The cure is to have the guests turn their cell phones off. It's not enough to have them hang up. Not enough to have them turn off the ringers. They have to be off the grid so they aren't sending/receiving packets from the local tower.

Not what you wanted to hear. Me either.
 
Bruce Watson said:
The cure is to have the guests turn their cell phones off. It's not enough to have them hang up. Not enough to have them turn off the ringers. They have to be off the grid so they aren't sending/receiving packets from the local tower.

Not what you wanted to hear. Me either.
Click to expand...

You're right, it's not what I wanted to hear. :/

Would a higher-quality system with diversity solve this? What are some other options?

Because, let's face it, we're not going to get the cell phones out of wedding ceremonies.
 
That is NOT cell phone interference. It is an RF "hit" resulting from interference from another transmitter near the frequency, multi-path reflections, or simply RF signal reduction. The solution is to make sure the transmitting and receiving antennas are fully deployed properly, make sure you are using fresh batteries, avoid frequencies close to other wireless mics or other wireless gadgets in the area, and have the transmitter and receiver as close together as practical.

Cell phone interference is much different. It is a much more man-made digital brrrup-brrrup-brrrup sound (typically sent in three bursts). Cell-phone interference is very similar to the radio jamming that communist totalitarian countries like the USSR (and the whole Eastern Bloc) used to do to keep their citizens from knowing what was going on in the rest of the free world.

What I heard in the example was a more "organic" loss of RF carrier kind of sound resulting from one of the causes outlined above. It sounds much more like what you hear on your car radio when you go through a tunnel or out of range from the radio station transmitter.
 
Richard Crowley said:
That is NOT cell phone interference. It is an RF "hit" resulting from interference from another transmitter near the frequency, multi-path reflections, or simply RF signal reduction. The solution is to make sure the transmitting and receiving antennas are fully deployed properly, make sure you are using fresh batteries, avoid frequencies close to other wireless mics or other wireless gadgets in the area, and have the transmitter and receiver as close together as practical.

Cell phone interference is much different. It is a much more man-made digital brrrup-brrrup-brrrup sound (typically sent in three bursts). Cell-phone interference is very similar to the radio jamming that communist totalitarian countries like the USSR (and the whole Eastern Bloc) used to do to keep their citizens from knowing what was going on in the rest of the free world.

What I heard in the example was a more "organic" loss of RF carrier kind of sound resulting from one of the causes outlined above. It sounds much more like what you hear on your car radio when you go through a tunnel or out of range from the radio station transmitter.
Click to expand...

Your description of the signal types is more in line with what I had in mind. I often hear that digital interference in crappy DJ equipment just before the culprit's phone begins to ring.

That said, the only thing I can imagine doing to improve my audio quality is be sure to use fresh batteries. Thanks.
 
Richard Crowley said:
That is NOT cell phone interference. It is an RF "hit" resulting from interference from another transmitter near the frequency, multi-path reflections, or simply RF signal reduction. The solution is to make sure the transmitting and receiving antennas are fully deployed properly, make sure you are using fresh batteries, avoid frequencies close to other wireless mics or other wireless gadgets in the area, and have the transmitter and receiver as close together as practical.
Click to expand...

Interesting. When I had this problem I was in a classroom over a co-op grocery store. Not another wireless microphone or other device in the area that I knew of. When I shot the establishing shot in front of the store, no interference. When I checked for a clear frequency in the class room, no interference. when I did a sound check before the class started, no interference. Once the students arrived and the class stared, interference.

The only thing that changed (that I could find) was the arrival of the students. It's possible that being up a story in elevation could have exposed me to RF from an outside source, but it's interesting that it only occurred for an hour, and in particular, only when students were present. How did it know???

Not saying it had to be cell phones. It would take some interesting and no doubt expensive equipment to find out for sure, and I don't have the resources or inclination for that. But what else arrives and leaves with people? Pagers, yes. What else? And yes, my batteries were fresh, and antennas deployed correctly and not covered up.
 
I agree with Richard, this sounds more like an RF dropout to me. Cell phones are a more rhythmic "bladdlap - bladdlap - bladdlap" rattling triple burst. This could be caused by the transmitter and receiver antenna not being parallel to each other, the transmitter antenna not being straight, the mic cable crossing the transmitter antenna, or multipath bounce within the room, among other things. Weak batteries, as previously mentioned, can also make it more likely - make it a practice to start EVERY shooting day with fresh batteries and if possible change them after about 4 hours of use.
 
To me it's indeed NOT the cellphone.

It sounds also like a problem in plugs (contacts).

But have you ever had that you're standing next to a radio, you move your hand in front of the antena...the radio sounds like "missing receivement". You do your hand down and it's ok again.
 
dre83 said:
To me it's indeed NOT the cellphone.

It sounds also like a problem in plugs (contacts).

But have you ever had that you're standing next to a radio, you move your hand in front of the antena...the radio sounds like "missing receivement". You do your hand down and it's ok again.
Click to expand...


You're right, it does sound like a dirty/faulty contact of some sort. However, based upon the condition of the system and the fact that he wasn't moving, I would base it on a power issue. I know that the batteries weren't fresh that day. (They weren't dead, but they weren't brand new).

From now on, I will also make sure the antenna is properly situated in the person's pocket.
 
leave antenna's out of the pocket, dont "fold" it in the pocket.

And also: don't expect big things from cheap wirelles things....(distance).

500$ = cheap
 
dre83 said:
leave antenna's out of the pocket, dont "fold" it in the pocket.

And also: don't expect big things from cheap wirelles things....(distance).

500$ = cheap
Click to expand...


I would consider a $500 system a mid-range. What makes & models would you consider high quality?
 
diversity receivement

wide range of receivement

settings like low/high cut filters, gain,

ability to see on the receiver that the battery of the transmitter is down
 
modus said:
I would consider a $500 system a mid-range. What makes & models would you consider high quality?
Click to expand...

$500 is rock-bottom for any kind of reliable wireless system. The minimum reasonable system is considered to be the Sennheiser G3 models. Anything less is an unreliable, fiddly, disposable, plastic toy. Professionals who do sound for major film and television projects use wireless systems that cost several thousand dollars each.
 
Richard Crowley said:
That is NOT cell phone interference. It is an RF "hit" resulting from interference from another transmitter near the frequency, multi-path reflections, or simply RF signal reduction.
Click to expand...

Probably not the OPs problem, but it's a maybe for mine. My problem occurred around dusk. Doing more research I've found that sodium and mercury vapor street lights are arc lights, and the arcs can create a fair amount of RF. Particularly from a failing lamp that tried to strike an arc repeatedly. So a street or security light could be the culprit some times.

I'm wondering about wi-fi -- this co-op grocery store may have been a local wi-fi hot spot for the convienience of their clientele. If they had a client show up for a coffee and to check email (with a leaky laptop) for an hour, that conceivably could have done it.

Ah, makes my head hurt. But at least I'm gaining an understanding of why wired mics are favored by so many. Wireless is wonderful when it works, but painful when it doesn't.
 
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