What is this **** beeping?
 

This is a clip taken from an office scene with overhead fluos, shot on an XL2 with an AT4073a and an AT40xx. I do not remember which channel is which.

Is it cell phone traffic? Whatever it was, neither the cameraman nor the boom operator heard it.

I'd almost describe it as a 'squeaking'.. More like a mechanical noise than an electronic one. Might be tape transport problems?

You think so? Would cleaning the head have helped? It did not happen in every scene, despite the fact that we used the same equipment. Perhaps it got worse over time?

To me, it sounds electronic. In particular, interference from something that is either transmitting an RF communication signal (wireless network, cell phone etc) or something digital operating at high frequency and with poor shielding (such as a computer).

Does it occur in specific locations in the office(s)? If so, it may give you a clue.

I can understand why it was detected during the shoot - it is very weak.

There were computers with LCD screens running nearby (it was an office scene, after all).

However, it also happened in other scenes featuring the same actor, so I think my cell phone hypothesis might be right.

Sounds very plausible. It reminds of when I have been on a conference call in a conference room with a wireless speakerphone, I would occasionally hear some beeps quite similar to yours and someone's cell phone would ring. It got to the point that I would say "Your phone is about to ring...."

My guess is that it is the cell phone talking back to the tower when the network is trying to establish a connection.

Now that I think about it, I can sometimes hear my girlfriend's cell phone do the same thing over her web camera. Why do microphones make it more audible?

The bad thing is that I already did a dubbing session with the actor and he probably had his cell phone on again :( The good news is that we have more dubbing sessions lined up, so I will sure to ask everyone to turn off their cell phones.

How do big productions cope with this problem?

That didn't sound like a cell phone to me. They usually produce a "brraaaap braaaap braaaap" kind of sound when they phone home. It sounds to my ears like something flowing through a pipe somewhere, maybe a noisy coolant pump in the air conditioning system. I hear it under a whirring-humming sound that definitely sounds like HVAC so I'd suspect it's also a part of the noise from the air conditioning system

They put in the contract that any powered-up cell phones within 100 yards of the location will be summarily destroyed <grin>.

Agreed. I'd know that sound anywhere; my CA sounds just like it--especially noticeable at night when I can't sleep. :)

Except there was no air conditioning in one of the locations.

Hi Emre......
 

Well, I've listened to that clip 20 times and thought it familiar, then I read your comment about "office scene" & "computers with LCD screens" and then it hit me - that sounds like the mute but distinct sound of an office chair return spring under load - like when you tilt back in the chair and then roll forward again - were there any within a bulls roar of the shoot and more to the point - were there any bums on one?

CS

You might also look for something a little less sophisticated. It doesn't sound electronic to me and it definitely doesn't sound like cell phone carrier being picked up by your equipment.

Does your soundperson have hanging earings? Or a noisy necklace? Or is there a loose bolt somewhere on your tripod/jib/crane? Were there two glasses on the desk that were just touching each other? Did one of the computers have a key hanging from the back of it? Or one of the crew have keys ? Was there a cat in the room? Don't laugh ... it's all possible.

The sound seems random, although the clip is short so there may be a pattern that isn't complete yet. But what I hear is mechanical and probably something inane.

Remember, you are the only one thinking of every possible scenario and problem during a shoot. The crew are just there for the food. So a soundperson wearing earings, necklace and charm bracelets wouldn't understand why they should be a problem.

Anyway, run the entire audio clip through a good editor that has noise reduction and that will suck it out of there.

My two cents ...

Tim

One final question. Were you using a 16xmanual lens in these shots?

Chris: There were office chairs, and people were sitting in them.

Tim: You are right that no-one thinks about it as much as I do.

Richard: We used the stock lens.

Here is another clip taken at another location and date. The only thing in common is one actor, the crew, and the camera. No air conditioning, fluos or office chairs; it's a bedroom scene.

I thank everyone who has contributed. Together we make a great team!

I just threw the file into ProTools and looked a frequency analyzer. It seems to be a modulated signal of 6349 HZ, There is also a steady tone of 16,000 HZ that is in audible. L and R channel are slightly out of phase.

To me it sounds like some sort of Radio Frequency telemetry interference.

I like this one. Makes me feel like I'm on board the Enterprise. :)

Does that mean the mics picked them up, or that they corrupted the audio in the XLR cables? The latter makes more sense to me, otherwise we should have heard the beeping too.

I wonder if everyone is hearing the same thing in this. I hear two clicks, the first slightly higher in pitch than the other, immediately followed by 'hooop' sound with a slight upward glissando, "cleeek...cliiiik......whooooeeeep, while running faintly under it in the background is a continuous ringing that sounds almost like a burlgar alarm bell ringing far far away.

The noise is below the room tone. I think it is mostly audible due to its high frequency compared to the room tone. So I would not be surprised if a sound guy with headphones did not hear it during the take. The approx 16 khz bump I am seeing might be the horizontal sync frequency from a monitor in the room. If that is the case, the XLR runs are probably picking up some crap.

Or then again, it could be a squeeky office chair :)

We posted at the same time. Emre, how long does the noise last? The sample we are listening to is very short.

Steve,

A while back you gave me some excellent step by step advice on syncing my Tascam to three cameras. The information you provided was detailed and written with patience. It really cleared up a confusing situation. Thanks.

OK...back to the mystery noise...

Spaces are full of noise. Most people never listen.

That sort of noise could be from anything plugged in.

I heard something like it in a conference room at the Dirksen Office building in DC last week. It was a plug in air purifier. I heard it in my cans, twisted the mic boom to find it and took my cans. Instantly it was a lot more obvious.

Also video lighting on dimmers can cause a mechanical vibration in some light fixtures that can sound soundthing like this.

There is good resaon to ask for quiet on the set. It allows the sound person to hear these sorts of sounds and hopefully deal with them.

Regards,

Ty Ford

Hmmm... Sounds like an outside low frequency (traffic) is causing and interior mechanical high frequency rattle.

Sounds like a spoon in an empty glass.

Glenn - you beat me to it! I was going to do the same thing today.

Short pulses of a highly coherent tone (i.e., the 16kHz tone) will sound like a click. Indeed, as the pulse gets shorter, it becomes more like white noise.

Trekkie-wise, it's an example of the Heisenberg Uncertainty Principle. As the duration of the tone gets smaller, the certainty of its frequency becomes less, too. Instead of a beep, you hear a click.

An application for the mythical Heisenberg Compensator Coils, perhaps.

There was a monitor in close proximity in both scenes! It sounded pretty quiet to me :(

If you listen carefully it sounds like the "Ode to Joy" played backwards. Perhaps it's the faint sound of Beethoven decomposing.

Here is a screensot that shows what I think is the video sync at about 16 kHz. I do not think that this is what you are hearing, but it does indicate that your mic line is picking up a signal.

To me the noise still sounds like two modulated tones one around 3000 and one around 6000. In fact you can see them as the smaller blips on the screenshot.

A 6000 Hz tone is pretty directional. If that was in the room I think someone would have noticed it when they got in a 'sweet spot'.

LOL! Upon further review with headphones on...the beeps sound more electronic and seem to move around in the stereo image. Unidentified Flying beeps.

Reminds me of a metal detector.

Not sure if a mixer is being used. It would be better to power the mic from quality mixer than from the camera input.

I just listened to it in headphones and it does sound electronic. I wonder if there might have been something on the tape before you used it? Play a new blank from the same batch. Then record something on the tape. That'll tell you whether the sound is coming from your equipment, or was present on the tape before you started.

If I had to describe the sound I would say it sounds like the capstan roller in the tape mechanism, but how you are getting it recorded to tape I don't know.

I love a good mystery ...

Tim

Tim,

We recorded on DV using an XL2. If the tapes were messed up, wouldn't it show up prominently in the video?

Depends what has contaminated the tapes, so to speak. It may not affect the video, don't know.

Since my last post I have done some more playing in the audio editor. If you filter out everything except 4K, then slow the track way down while maintaining the pitch, the sound starts to become familiar. It sounds like a modem communicating. Now at regular speed, it doesn't, it's much higher in speed and frequency. Sort of like what DSL high-speed sounds like. The office scene most likely would have had DSL present in the room ... did the bedroom? Remember, the DSL signal is present on the phone lines whether the computer is on or not. If you had microphone cables laying in proximity to telephone wires then they could have picked up the signal.

Anyway, that's all the guesses I have.

Been in the audio business a long time and we have a saying ...

If it don't work ... it's a cable.

After you have checked everything twice and it still don't work ... it's a cable.

And when you are sure that every cable and every connection is perfect and it still don't work ... it's a cable.

Best of Luck ...

Tim

We have cable at home, not DSL. I do not know which of the two the office had.

Yet your point brings me back to my cell phone hypothesis. That is a form of modem too. I just do not understand how it could affect the signal running through the XLR cables.

"Pin 1 Error"
 

The answer to this is a condition called "pin 1 error" that exists in some XLR audio equipment including microphones and mixers. It works like this. The device is ostensibly shielded from RF by its metal enclosure, but this protection is foiled by a bad wiring decision. Internally, the XLR cable shield (pin 1) lead runs from the device's connector to the "ground" area of the device's circuit board. In turn, the ground area of the circuit board is connected by a short lead to the outer metal housing. The erroneous thought is that this is equivalent to connecting the shield directly to the housing. Instead, the short internal lead becomes a little broadcast antenna inside the device for the RF signal picked up the cable shield. The proper way to terminate the XLR cable shield is at the external interface with the device's housing.

I don't know if your problem is cell phone interference, but if it is, that's almost certainly how it is getting in.

If you do a search on pin 1 error you'll find, as I recall, where the original discoverer of this condition uncovered it in some big name microphones.

Forgive the second post, but the science teacher in me is forcing me to say that a hypotheses begs an experiment. If you don't want to tear into your equipment to inspect the wiring, I'd put a cell phone (or two or three) right next to an XLR cable and turn them on while listening with phones. If I got the noise, I'd try obvious stuff like disconnecting the mic, etc.

Fascinating... so that means my Audio Technicas are poorly shielded? I will have to try taking a bunch of cell phones and putting them next to my mics some time, to confirm the hypothesis, unless somebody has already tried.

edit: You beat me to it. Great minds think alike!

It may be cell phones and I'd certainly do the experiment but most of the time cell phone interference is intermittent. The phones 'call home' every few minutes to let the system know where they are but it's not continuous data traffic unless they're actively in use.

Only a good experiment could determine whether your AT's are poorly shielded.

I once queried AT as to whether my AT3031's might be wired with pin 1 error. Their reply was that they never had a complaint about pin 1 error, but didn't answer my question directly.

It would be good to use cell phones of different brands because of their differences. Here's a thread where cell phone interference was discussed, and where Sam Gates very politely enlighten me about pin 1 error: http://www.dvinfo.net/conf/showthrea...ight=pin+error

The beeps seem to be flying because his recording is slightly out of phase. Left channel is ahead of Right channel. The beeps are in Stereo! In fact all the audio on the sample is out of phase. Are there two XLR runs?

There are two mics running into the same camera.