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  #1  
Old 2008-04-12, 04:39 AM
cobain72 cobain72 is offline
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Strange frequency

Hi,

can anyone tell me, what's that strange 'line' at 19000hz is. How comes the origin??

http://img518.imageshack.us/my.php?image=freqzq9.jpg

Thanks
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  #2  
Old 2008-04-12, 05:55 AM
ameyer17 ameyer17 is offline
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Re: Strange frequency

That'd be a FM-sourced recording.
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  #3  
Old 2008-04-12, 09:10 AM
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Re: Strange frequency

Quote:
Originally Posted by cobain72 View Post
Hi,

can anyone tell me, what's that strange 'line' at 19000hz is. How comes the origin??

http://img518.imageshack.us/my.php?image=freqzq9.jpg

Thanks

19kHz tone is used by the FM transmission system in the US to alert the receivers to decode the mux into two channel stereo.
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Old 2008-04-12, 09:24 AM
cobain72 cobain72 is offline
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Re: Strange frequency

Quote:
Originally Posted by jameskg View Post
Quote:
Originally Posted by cobain72 View Post
Hi,

can anyone tell me, what's that strange 'line' at 19000hz is. How comes the origin??

http://img518.imageshack.us/my.php?image=freqzq9.jpg

Thanks

19kHz tone is used by the FM transmission system in the US to alert the receivers to decode the mux into two channel stereo.
But why is above 19kHz nothing cut? Btw the freq is from a dat recording thats why i find it strange. My first thought the mp3 file was re-recorded with a md and then converted to flac
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Old 2008-04-12, 09:57 AM
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Re: Strange frequency

if you'll notice, the audio stops around 15kHz (limit of FM transmission system). All the junk above 15kHz has probably come from effects being applied to the recording after transmission - EQ, reverb, stereo "enhancing", etc. Notice the non-linearity of the spectrum after 15kHz... it's all artificial enhancement, I'd say. If it was on DAT, it probably was sourced from FM before that.

That audio abouve 15kHz is likely junk... try filtering high-pass at 16kHz and see what you hear. Won't be much, if anything, I'd bet.

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  #6  
Old 2008-04-12, 11:40 AM
cobain72 cobain72 is offline
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Re: Strange frequency

Ok thanks for your help, much appreciated
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  #7  
Old 2008-04-13, 03:42 PM
ameyer17 ameyer17 is offline
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Re: Strange frequency

Actually, everything above 15 kHz except the 19 kHz tone would probably just be noise.
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