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Old April 22nd, 2005, 02:48 PM   #1
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Two audio questions...

1. The first question is a (minor) problem.

I own a Sony Z1E and just bought a Sennheiser ME66 mic.
I tested it this morning in HDV mode, recording some birds outside.
I put the audio and video in Sony Vegas 6 and wanted to do some noise reduction (the audio is very clear, but there was some background noise).
I put the audio into Audition just trying to get the background noise out, but when I watched the spectral view I notised something.
There is some static noise at different frequencies.
I (almost) can't hear them I think, I think I know how to get them out in post, but is there a way to avoid them while recording?
It is no noise from 'outside' the camera, it has to be the mic/tape noise/camera noise or something.

See the horizontal lines in the following picof the spec. view:
http://www.eclectus.nl/freq.jpg

2. Second question.

When recoring with my me66 I think it's pitty I only record on one track (mono).
What mic. can I use for recording background 'noise' on the second track (somewhat stereo)?
I wil mainly use it outside.

Thanks!
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Old April 25th, 2005, 10:45 AM   #2
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Can't anyone help me??
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Old April 25th, 2005, 10:50 AM   #3
 
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your image isn't coming up, so can't see what you have there.
If you've recorded the signal too low in the Z1, you may be seeing compression artifacts. MPEG 1/Layer 2 audio needs level so that it has something to work with. that would be my first concern.
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Old April 25th, 2005, 12:56 PM   #4
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I can describe the pic.

Between 0 - 8000 hz. you can see the recorded audio (think it was a bird singing in the distance).
But there are horizontal lines at:
5900 / 7700 / 9000 / 10500 / 12000 hz.
And a few less bright at:
15000 / 16500 / 18000 / 19500 / 22700 hz.

I have no idea where it is comming from.
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Old April 26th, 2005, 03:55 AM   #5
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Spot: the picture is working fine for me, can you try again?
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Old April 26th, 2005, 09:26 AM   #6
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Can you try the mic off camera to see if its picking up from rear ,camera sounds? drive motor, etc.Does the noise go away w/mic off camera?
Why are you sure it is not external noise?
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Old April 27th, 2005, 08:03 AM   #7
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I have tried the mic. about a meter away.... still the same.
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Old April 28th, 2005, 12:25 PM   #8
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To make things a bit more complicated.

This is a sample from audition spectral view captured with sony vegas 6 internal cature feature in hdv mode:
http://www.eclectus.nl/freq_m2t.jpg

This is a sample from audition spectral view captured with sony vegas 6 external capture feature in dv mode (camera hdv->dv).
http://www.eclectus.nl/freq_dv.jpg

In dv mode all weird 'noise' gone!
I really don't understand this.....does anyone understand?
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Old April 30th, 2005, 11:11 AM   #9
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So nobody has any idea.....too bad :(
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Old April 30th, 2005, 11:22 AM   #10
 
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I've never been able to get your images to open, otherwise, I'd be happy to help.
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Old May 1st, 2005, 04:48 AM   #11
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It's quite interesting that all these frequencies happen to be multiples of 1500Hz.

Are you sure that those lines are "continuous" lines? What if it's not a superposition of all those frequencies but alternating frequencies?

Maybe some "inaudible" high freqency noise that the compression samples down? MPEG image compression at least is interframe compression... Maybe it messes with the sound too, as suggested in a previous post?
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Old May 1st, 2005, 05:13 AM   #12
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...and the sampling rate was - let me guess - 48kHz? That's 1500Hz times 32...
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Old May 1st, 2005, 06:24 AM   #13
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Here are the pictures on tripod:
http://blaatschaapje.tripod.com/audio_error/

As far as I know, the samplerate was 48kz.

I just captured video into Vegas with the internal program.
I right clicked the audio line and opened it with audition.
I did the same with the captured dv video, but no problems at all.
The lines are all the way through the clip (about 20 min.)

How can I get rid of this??
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Old May 1st, 2005, 09:19 AM   #14
 
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I wonder if you have some sort of electronic interference that the cam picked up? I have no idea from what, but I've seen this on non-HDV recordings due to high freq radio in the early days of DAT.
I don't know the correct answer, but Ralf hits on what is the first clue. I don't believe it's compression error, or there wouldn't be the consistency from the bottom to the top. Were it compression, it should be lesser in the lower freqs and more in the top.
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Old May 1st, 2005, 12:50 PM   #15
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I just tried to record 2 min. of the footage in dv and hdv.
I put the cam on my table and didn't touch it except for changing the hdv to dv option.
I get the same results, dv is perfect hdv a lot of stripes!
It's the same cam on the same place with the same video...
Darn!
Is recording (the audio) in hdv more sensitive for electronic interference then in dv mode?
I really don't understand it...
I just want to get rid of it.
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