Cell phone, or Nokia radio phone? Recent post on noise with wireless mics.

My wife walks thru the room talking on her cell and my sub woofer goes nuts.

The footage is from 2 seperate weddings and I did not have a phone on. It is not the same kind of sound as when your cingular wireless phone is about to ring and your speakers make that noise. This is a consistent pitch (high pitch) that lasts for less than half a second and always shows up in the same place when dealing with the footage, but if I play it on my set top or on another computer, it is not there. If I mute that one track, it is not there. This is quite strange to me.

j razz

Not using any unregistered / demo audio effects? E.g. Sony Noise Reduction beeps if not registered.

Have yout tried to move the audio in timeline, i.e. does the beep follow the source material or the exact timeline position?

What if you copy the audio to new track and mute the source?

When you say "always shows up in the same place" what specifically do you mean?
Do you mean always from the G2?

If so then OK, logic suggests the beep is being recorded by the camera because the camera got fed audio with a beep in it!

Now why is that happening?

Well that's going to be tricky, it could be the receiver picking up something or it could be the transmitters audio section picking it up.

Does this beep only happen once or more than once, does it last very long?

Once you know where it is on the T/L it should be easy enough to get a good bead on it in say SF, select just the section of the channel with the beep and use the spectrum analyser. Once you know specifically the frequency a narrow notch filter on just that section and you should be rid of it.

Also knowing the specific frequency would be a help in knowing more about how to stop it in the first place.

Also which model G2?

We only use the 500 series, way better than the 100s and a lot more expensive, 8 systems in service and no beeps.

Also a bit of a trap, the cabling from the receiver to the camera is tricky and also you can cause the receiver to get gnarly if you feed it phantom power. What camera is the receiver connected to?

Bob.

EDIT:

If all this stuff with SF is a bit much email me the bit with the beeps and I'll have a look at it. I should be able to fix it and email it back to you minus the beep. Just render out a few seconds either side, put some markers so you know exactly where to patch it back. Render it out native (NO mp3 etc).

Nope. No unregistered anything. No plugins are being used that were not automatically added by Vegas and what is on the g2 100 track is also on the other 5 tracks.
The beeps are always in the same place time and timeline-wise. If I mute the track the beep dissappears. If I play the same audio track on another computer, the beep dissappears. If I play the audio on a set top player, the beep dissappears.
I guess I should also clarify the beep b/c it is not really a beep. It is of the same type of noise as if you have a monitor that is going wack and gives off that high pitch noise. The only difference is that this is not always on. It "beeps" randomly throughout the entire audio track- when there is audio on the track. And to the best of my memory, if the track is there and there is a flat line of audio, there is no beep. Give a little sound coming through the mic and there is the beep again.
It seems to me that the computer is picking up noise on this one channel and choosing to add a high-pitched beep. I can't explain why and maybe I am wrong. Maybe I just don't hear it on the other 2 computers or set top b/c the speakers are not as good? I will run some more tests soon to see. I don't think this is a one time thing as it is on the footage from the previous two weddings I shot (or at least, my computer likes to add it to the g2 audio track).
John Meyer did a spectrum analysis of it and could not see or hear what I could plainly hear. When I zoom in on the timeline right where one of the beeps are that I can hear, it is not there in waveform. Still confused as ever.

j razz

Link to previous post with audio link.

Farss, above is a link to a previous post that I included an audio sample. It is in wmv I think and is towards the bottom. Like I stated earlier though, John Meyer couldn't find anything in the audio stream and neither can I. If you would like though (and I appreciate the offer) I will send you an uncompressed snippet in wav format.
Thanks for the offer, but for some reason, I don't think you will find anything.

j razz

I might have the answer!

All the G2 series units use a pilot tone to lock the receiver. I don't know what frequency that is but I'm wondering if that's causing either aliasing or a heterodyne, possible just through the soundcard on that one system.

Obviously the pilot tone is outside the audible range but wierd things can happen with digital audio.

Bob.

You might be right, but I have never "heard" a pilot tone. I was under the impression it was a constant- not a beep. I was also under the impression that if you hear something on audio, you should see it in the wave form too- but that also is a misnomer.

After I do a little more testing to make sure I have my ducks in a row- I am going to shoot Sennheiser an email and reference this thread. Thanks Bob.

j razz

Is the tone you are hearing actually coming from your SPEAKERS or are they coming from the computer itself?

I ask because I sometimes hear real soft tones coming from my computer when data is being processed.

Dave T2

Speakers. If I mute the track, it is gone. If I turn up the audio, it is louder, etc. Thanks for the thought though.

j razz

Bob,

You beat me to the punch! I was just formulating a pilot tone answer when I got to your response.

I've heard that kind of thing on our Lectrosonics IFB systems that use pilot tones for the audio compander. It appears to happen in high multipath situations. I don't know if the multipath causes an audible audio hetrodyne because of the mixing of the primary and delayed signal or not. As the transmitter or receiver (or people for that matter) move araound, the multipath can change, causing variations in the effect. Think of ghosting distortion on a TV set with over the air reception with rabbit ears.

The odd thing about this is the fact that it can't be heard on the same file on different systems, but it does seem to correspond directly with the wireless mic tracks. That's what's confusing the issue. I didn't hear it on the sample I downloaded last week, but jrazz could - odd. It might be the way the sample was generated or possibly the differing frequency response of the systems we are listening on.

My bet's on the wireless system. It's a miracle the darn things work as well as they do ( . . . . he said, knowing that he's got a 7 wireless mic shoot coming up Friday!)

Wish I could hear the problem. Is there any way you can post just the wireless track as is?

Tom

Once I get back to the editor (in about 8 hours or so) I will make a veg file to just include that one track and zip it up with the clip attached and post it for download. I will take a small portion from the whole where I can hear the beeps so as not to make a big file.
Maybe I just have super good hearing- even better than the waveform generator can generate.... yeah right- if that was true, I should be working for homeland security:)

j razz

Here's the thing and it's a lot of supposition on my part.

The pilot tone is supersonic (over 20KHz)
The Nyquist frequency for DV audio is 24KHz.
Poorly designed audio systems might have issues with frequencies close to or even above the Nyquist frequency. You don't normaly hear or see anything (no beeps) during silence cause the problem is due to creation of harmonics, you need a bit of the pilot tone and something else.
The problem isn't heard in rendered output possibly becuase Vegas resamples the audio applying correct low pass filtering and removing the pilot tone remnants.
As the problem frequency is above 20KHz the SA in SF will not show it, it pegs out at 20KHz.
It cannot be heard on most systems because the sound card handles it properly.

A few tests you could try:

1) Change the projects audio properties to 44.1KHz. This forces Vegas to resample the audio before it gets sent to the sound card which will now be clocking at 44.1KHz.

2) Leave the Project audio properties at 48KHz and apply a small amount of HF roll off (the reduce tape hiss preset would do under track Eq) to the problem track. This again will cause resampling.

3) Just render the problem track to a new file of the same properties and bring that back in as a substitute audio track.

I suspect the problem possibly starts with the audio section in the camera, quite likely Sennheiser and others assumed the pilot tone would get killed by the low pass filters in any recording device.

I should be attending a sales pitch with the gurus from Sennheiser next week, I can bring this up with them directly.

Bob.

Here is the link to the veg and trimmed media.
it's got about a minute and a half left for upload and is about 50megs.

j razz

OK, I hear a very faint beep at three locations. The one that is easiest to isolate is at 5.5 seconds into the VEG file version of your clip. I copied the audio into SoundForge and isolated the sound at about 8,600 Hz, with a second spike at around 12,900 Hz. It took a little digging, but I found that the pilot tone frequency on a G2 is 32.768 kHz. Spurious mixing signals are usually generated by either the sum or the difference between the main tone and the mixing tone. I'd have to know a lot more about the design to see if there is another signal at an offset from 32.768 of either 8.6 or 12.9 kHz.

However, as Bob already suggested, if you can defeat the pilot tone (which the specs say you can do), I'd try that and see if the problem goes away.

Yip,
I'm seeing the same thing in SF.
32KHz should not make it past audio A->D converters unless they're running at 96K.

The more interesting thing is looking at the whole file there is something all the way upto 23KHz, it's down a long way after a serious drop around 15KHz. There's a couple of tiny peaks in there as well, might be nothing, might hold the clue.

Bob.

Yep, I can turn the pilot off and it should have no ill effects as I leave the g2 on the whole time anyway so there should be no popping. Still though, it doesn't make much sense and I have another wedding this weekend. I will play around with it on Friday to see if turning off the pilot will get rid of the sound- if not, I will use the other mic.
Bob, let me know if you are going to bring this up- I will leave the sample up on my site if you are. If not, I will contact Sennheiser and see what they say.

Guys, I really do appreciate the fact that you have taken the time to look into this problem that does not affect you, to help me. Much appreciated.

j razz

32KHz should not make it past audio A->D converters unless they're running at 96K.

Definitely true, but what sometimes happens is that you get beats (mixing products, basically) with other nearby frequencies or with the sampling circuit. If contacting the manufacturer, measure the time between each beep (about 3-4 seconds I think). That should help them determine whether their equipment is involved. The actual frequencies of the beeps is probably not useful, since that may be caused by the interaction of their signal with your capture circuitry.

Well it does affect me indirectly, company I work for is a Senny reseller and we do use a lot of their G2 500 kits.

I could possibly simulate this by getting SF to create a 32KHz tone (@ 96K sampling) and drop that into a 48K audio project.

Bob.

Okay, I have filmed a few more times since the beep incident. I turned the pilot tone off and voila- no more beeps.

Bob, did you ever talk to Senny about this?

j razz