Two audio questions... at DVinfo.net

Johan Manders · April 22nd, 2005, 01:48 PM

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!

Johan Manders · April 25th, 2005, 09:45 AM

Can't anyone help me??

Douglas Spotted Eagle · April 25th, 2005, 09:50 AM

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.

Johan Manders · April 25th, 2005, 11:56 AM

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.

Rob Lohman · April 26th, 2005, 02:55 AM

Spot: the picture is working fine for me, can you try again?

Jack Smith · April 26th, 2005, 08:26 AM

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?

Johan Manders · April 27th, 2005, 07:03 AM

I have tried the mic. about a meter away.... still the same.

Johan Manders · April 28th, 2005, 11:25 AM

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?

Johan Manders · April 30th, 2005, 10:11 AM

So nobody has any idea.....too bad :(

Douglas Spotted Eagle · April 30th, 2005, 10:22 AM

I've never been able to get your images to open, otherwise, I'd be happy to help.

Ralf Strandell · May 1st, 2005, 03:48 AM

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?

Ralf Strandell · May 1st, 2005, 04:13 AM

...and the sampling rate was - let me guess - 48kHz? That's 1500Hz times 32...

Johan Manders · May 1st, 2005, 05:24 AM

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??

Douglas Spotted Eagle · May 1st, 2005, 08:19 AM

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.

Johan Manders · May 1st, 2005, 11:50 AM

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.

April 22nd, 2005, 01:48 PM	#1
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	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!

April 25th, 2005, 09:50 AM	#3
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	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. __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

April 26th, 2005, 02:55 AM	#5
Rob Lohman RED Code Chef Join Date: Oct 2001 Location: Holland Posts: 12,514	Spot: the picture is working fine for me, can you try again? __________________ Rob Lohman, visuar@iname.com DV Info Wrangler & RED Code Chef Join the DV Challenge \| Lady X Search DVinfo.net for quick answers \| Buy from the best: DVinfo.net sponsors

April 30th, 2005, 10:22 AM	#10
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	I've never been able to get your images to open, otherwise, I'd be happy to help. __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

May 1st, 2005, 08:19 AM	#14
Douglas Spotted Eagle VASST Join Date: Jan 2004 Location: Stockton, UT Posts: 5,648	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. __________________ Douglas Spotted Eagle/Spot Author, producer, composer Certified Sony Vegas Trainer http://www.vasst.com

April 25th, 2005, 09:45 AM	#2
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	Can't anyone help me??

April 25th, 2005, 11:56 AM	#4
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	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.

April 26th, 2005, 08:26 AM	#6
Jack Smith Major Player Join Date: Nov 2003 Location: ontario Posts: 445	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?

April 27th, 2005, 07:03 AM	#7
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	I have tried the mic. about a meter away.... still the same.

April 28th, 2005, 11:25 AM	#8
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	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?

April 30th, 2005, 10:11 AM	#9
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	So nobody has any idea.....too bad :(

May 1st, 2005, 03:48 AM	#11
Ralf Strandell Regular Crew Join Date: Jan 2004 Location: Europe Posts: 180	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?

May 1st, 2005, 04:13 AM	#12
Ralf Strandell Regular Crew Join Date: Jan 2004 Location: Europe Posts: 180	...and the sampling rate was - let me guess - 48kHz? That's 1500Hz times 32...

May 1st, 2005, 05:24 AM	#13
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	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??

May 1st, 2005, 11:50 AM	#15
Johan Manders Regular Crew Join Date: Jan 2005 Location: The Netherlands Posts: 50	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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