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cobain72
2008-04-12, 04:39 AM
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

ameyer17
2008-04-12, 05:55 AM
That'd be a FM-sourced recording.

paddington
2008-04-12, 09:10 AM
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.

cobain72
2008-04-12, 09:24 AM
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

paddington
2008-04-12, 09:57 AM
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.

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

cobain72
2008-04-12, 11:40 AM
Ok thanks for your help, much appreciated :)

ameyer17
2008-04-13, 03:42 PM
Actually, everything above 15 kHz except the 19 kHz tone would probably just be noise.