Sound artifact

[David Trayers]

I have two XL2 cameras and I get this on both cameras. It doesn't matter whether it's the onboard mic or an external mic connected by XLR.

It's this very random and occasional 'chhhip' noise. It can be on both channels or one. It's random.

I put a small audio clip on my web site and the sound is just about in the middle of the clip.

XL2 Sound

Have you heard a similar sound? Could it be dirty heads?

Thanks!

Dave

[Chris Soucy]

Hi, David...................

Well, dirty heads is pretty well out, unless you're getting screwed video at the same spot, which, as it hasn't been mentioned, I guess you're not.

Sounds to me like an EMI hit from something, somewhere.

The reason it wouldn't effect the video is that it's digital from the word go, right off the sensors.

The audio, on the other hand, is analogue until it hits the AD converters in the camera before being merged with the digital video signal to write to tape.

As such, it's susceptble to EMI, which the AD converters simply transcode to digital.

The fact that both machines display the same behaviour almost guarantees it is not a camera problem but external.

The usual suspects are: any polling mobile device - phone, blackberry, the list is endless (don't keep your mobile anywhere near either the camera or mic cabling!).

Local radar (you live/ shoot near a military air base?), tv or radio transmitters, even plug in power packs having bad hair days.

As it seems to be following you around, it's quite possibly something to do with you, your gear, your shooting habits etc etc etc.

Time to play Sherlock Holmes and track it down.

There must be something in common with every occurance, figure out what that "in common" is and you've cracked it.

Oh, and do listen to your audio on a pair of cans whilst you shoot, so you know instantly when it happens, otherwise you've made it a dificult search.


CS

[David Trayers]

Thanks for the reply, Chris.

I think you may be on to something.... the video is great, so you're probably right about the heads being ok.

The 'chip' sound doesn't happen on both cameras at the same time... I typically shoot with both simultaneously and do a multicamera edit in Premiere and usually it's one camera or the other. Usually one camera is using the onboard mic as a safety and the other uses an external mic some distance away or I'm getting a feed from the house mixer.

I monitor the camera using the external mic or house feed with headphones and I don't recall ever hearing the chip over the cans. That's why I was thinking it was *after* the audio inputs and may happening during the recording process. Does the audio over the headphones come before the recording head or after (like the old three head cassette players)? In other words, am I monitoring the audio signal sent to the head or the actual recording on the tape? I would think it's the signal sent to the recording head. For my next shoot I'll pay more attention.

I *have* heard over the cans a buzz introduced by my call phone when it drops out of 3G service. I hear the same thing on my computer speakers when the phone is near them. It's a known issue with my phone so I've learned to turn it off while shooting. But this 'chip' sound is nothing like the interference sound from the cell.

I mostly shoot dance recitals and school performances... there is a prohibition of flash photography during these performances but parents do it anyway... I'll go back an see if there could be a correlation between the camera flashes and the 'chip' sound. I also shoot performance stills, so I'm sensitive to performance photos without flash and would think I would notice if the 'chip' corresponds with a flash, but I'll have another look.

I'll also review my setup next time and see if there is a common source between each camera. Thanks again.

[Chris Soucy]

From what I know, what you're hearing on the cans is what goes into the A/D converters on the cam, not what is recorded on the tape, tho' what can possibly go wrong between one and the other would have to be pretty esoteric, to be frank (tho' not impossible, mind)

If you're shooting with a mic "off camera", that has to be suspect numero uno, right there.

Bad connection, cable, incorrect wiring, ripple AC commands on the mains voltage (do you guys have ripple control on the mains? Sends our capacitive "touch lamps" loopy here), you name it, the skies the limit.

Doubt it's a flash photography issue, it's too long for that, what I'm hearing is a sustained 300 millisecond burst, which is way too long for any flash gun to emit, that I am aware of.

Keep at it Sherlock.


CS