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  #1  
Old 08-29-2017, 01:24 PM
daeron80 daeron80 is offline
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Default High pitched tones in recording from Germany

The video team from my department just returned from Germany where they recorded a large number of videos in a variety of locations - old churches, castles, outdoor settings, etc. They recorded using Sanken lapel mics, Lectrosonic transmitters and receivers set to frequencies that are safe in many part of the US, and a SoundDevices 702 tracking to SD card. We use this equipment relentlessly here in the States and get excellent results.

But all the files that came back from Germany contain a set of constant tones at 3120 Hz and its harmonics. They are just loud enough to be noticed in the silences between words. iZopope RX handles it fine. But just curious. Any idea what could have caused it?
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Old 08-29-2017, 01:37 PM
Darryl Ramm Darryl Ramm is offline
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Default High pitched tones in recording from Germany

Do you have access to the recorder and Mic... I would test them again. And test exactly as used.

Make sure to check exactly what was done, e.g. was an external power supply or firewire connection used... if so they are your main suspects. If that is not it then something else the crew was using,.... since seen at multiple sites. First interference suspect is going to be GSM buzz, but this is different than you are reporting.


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Last edited by Darryl Ramm; 08-29-2017 at 01:48 PM.
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Old 08-29-2017, 04:13 PM
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Default High pitched tones in recording from Germany

Quote:
Originally Posted by daeron80 View Post
The video team from my department just returned from Germany where they recorded a large number of videos in a variety of locations - old churches, castles, outdoor settings, etc. They recorded using Sanken lapel mics, Lectrosonic transmitters and receivers set to frequencies that are safe in many part of the US, and a SoundDevices 702 tracking to SD card. We use this equipment relentlessly here in the States and get excellent results.

But all the files that came back from Germany contain a set of constant tones at 3120 Hz and its harmonics. They are just loud enough to be noticed in the silences between words. iZopope RX handles it fine. But just curious. Any idea what could have caused it?


If anything at all was plugged into mains power, I would suspect the power converter dumped noise that coupled through the grounds.


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Old 08-30-2017, 07:02 AM
daeron80 daeron80 is offline
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Default Re: High pitched tones in recording from Germany

Thanks for the replies. Some of these files were recorded on a cruise ship on the Rhine River, some outdoor using only battery power, and some in old buildings in various cities along the Rhine. Identical problem everywhere, same frequencies and intensities. First chance I get, I'll see if I can replicate it with the same gear. But I know it was working right the day before they left here to go to Germany.
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Old 08-31-2017, 03:40 AM
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Default Re: High pitched tones in recording from Germany

Quote:
Originally Posted by daeron80 View Post
... Germany ...Lectrosonic transmitters and receivers set to frequencies that are safe in many part of the US
What were the frequencies set to in the Lectros ?
Do all recordings contain the high pitch tone or just the recordings from one of the receivers ?
Was the "free-frequency-scan" done with the reveivers ?
Was any other equipment used like a wireless video transmitter from the camera to external monitors ?
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Last edited by joachim; 08-31-2017 at 05:05 AM.
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Old 08-31-2017, 04:56 AM
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Default Re: High pitched tones in recording from Germany

Reading this got me to thinking in ham radio terms and various squelch systems. It's not CTCSS which are low in frequency (top out at 203 HZ). That 3120 HZ (if that number is accurate) is more in the range of something like what the selcall system https://en.wikipedia.org/wiki/Selcall
system uses. Even that doesn't have a freq that goes as high as what's been measured.

I'm willing to bet the culprit is not in the system that did the recording but some kind of squelch system external to the capture electronics.

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Old 08-31-2017, 07:39 AM
daeron80 daeron80 is offline
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Default Re: High pitched tones in recording from Germany

Since no audio person went on the trip, it's difficult to know what all happened. We weren't even consulted, sadly. The video guy took some of the equipment we usually use for location recordings and used it as-is. I'll have to wait for the equipment to be returned to get the exact wireless frequency, but it was in the 400-500 MHz range.

RX has a good Spectrum Analyzer. Your pointer will snap to high amplitude components and read out the exact frequency. I set the FFT to 16348. The tone is similar to a gently distorted, filtered square wave with a 3120 Hz fundamental. Strong odd harmonics, much softer even harmonics. Steady pitch, with amplitude slightly modulated by the signal.

Here's a screenshot of a portion of one of the files.
https://www.dropbox.com/s/t59p3qe7ug...tones.png?dl=0
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Old 08-31-2017, 02:39 PM
musicman691 musicman691 is offline
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Default Re: High pitched tones in recording from Germany

Quote:
Originally Posted by daeron80 View Post
Since no audio person went on the trip, it's difficult to know what all happened. We weren't even consulted, sadly. The video guy took some of the equipment we usually use for location recordings and used it as-is. I'll have to wait for the equipment to be returned to get the exact wireless frequency, but it was in the 400-500 MHz range.

RX has a good Spectrum Analyzer. Your pointer will snap to high amplitude components and read out the exact frequency. I set the FFT to 16348. The tone is similar to a gently distorted, filtered square wave with a 3120 Hz fundamental. Strong odd harmonics, much softer even harmonics. Steady pitch, with amplitude slightly modulated by the signal.

Here's a screenshot of a portion of one of the files.
https://www.dropbox.com/s/t59p3qe7ug...tones.png?dl=0
I still think it's some kind of continuous control tone that your system picked up. Might even turn out to be a digital control stream. Not that familiar with what's used over in Europe.
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Old 08-31-2017, 03:51 PM
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Default Re: High pitched tones in recording from Germany

I would be willing to bet that it is some recently developed defect in the recording equipment, since the problem occurred in multiple places and on battery power and on AC power. But I don't pretend to know anything about the devices used that you detailed.

Are you able to EQ or otherwise edit the noise out of the recordings?
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