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rhythmic noise on a CD or CDR
krabapple
post Mar 24 2006, 00:03
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Ever have a CD or CDR that sounds sort of like a scratched LP, in that it has a rhythmic ticking or clicking or crackling sound (not part of the music!), possibly getting worse on later tracks on the disc? Even when there doesn't appear to be any defect on the disc surfaces?

What causes that?
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ameyer17
post Mar 24 2006, 00:40
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QUOTE (krabapple @ Mar 23 2006, 05:03 PM)
Ever have a CD or CDR that sounds sort of like a scratched LP, in that it has a rhythmic ticking or clicking or crackling sound (not part of the music!), possibly getting worse on later tracks on the disc?  Even when there doesn't appear to be any defect on the disc surfaces?

What causes that?
*

Faulty pressing or bad burn? Unless it's intentional, of course.
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spectacle
post Mar 24 2006, 00:44
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I'm not the only one then...

I'm not through with testing but check:

http://www.hydrogenaudio.org/forums/index....showtopic=42671
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AndyH-ha
post Mar 24 2006, 01:25
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I doubt it applies to any performances from recent years, but commercials CDs sometimes have an LP or 78 as their source. If it could be one of these, perhaps someone just didn't do a good job of cleaning it up.
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CiTay
post Mar 24 2006, 01:58
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This comes from your CD player, that sound is not on the CD. But the CD has errors which get worse towards the outer area (the outer areas of a CD traditionally have more errors for various reasons). So your CD player fails to cover up the read errors and then you hear those crackling sounds. A different player might read it fine (or interpolate better) so you won't hear any crackling. But usually those sounds tell you that it's time to re-burn that CD, or get a different CD player that is more forgiving towards suboptimal CDs.
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Pio2001
post Mar 24 2006, 15:35
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CDRs becoming unreadable exhibit this behaviour. The damage is bigger on the outer part, which is the end of the audio track, and as it is located asymetrically, you get scratchy sounds for every rotation of the CD.
I've got a sample at home. I'll post it when I'm back.

If this is indeed a CDR loosing its content, it is much too late to recover the original data when the errors are audible like this.
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krabapple
post Mar 25 2006, 00:28
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QUOTE (Pio2001 @ Mar 24 2006, 09:35 AM)
CDRs becoming unreadable exhibit this behaviour. The damage is bigger on the outer part, which is the end of the audio track, and as it is located asymetrically, you get scratchy sounds for every rotation of the CD.
I've got a sample at home. I'll post it when I'm back.

If this is indeed a CDR loosing its content, it is much too late to recover the original data when the errors are audible like this.
*


I guess I'm wondering, what causes a CDR to become unreadable, to lose its content, but mainly in its outer circumference?What's the mechanism behind this?

This post has been edited by krabapple: Mar 25 2006, 00:28
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Sunhillow
post Mar 25 2006, 02:11
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The rhythmic ticking can be a mechanically generated noise. It comes from the lens tracking mechanism, when something obscures the track, e.g. a dust particle.
Wipe the CD with a soft cloth, ans in most cases the ticks will disappear.
When a CDR becomes unreadable, the distortions come out of the speakers.
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singaiya
post Mar 25 2006, 18:22
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If it's a pressed CD that shows this behavior, it could be disc rot, where the bottom side turns a bronze color. This was due to some dye used by a certain UK manufacturer in the late 80s-early 90s. I have a Skullflower CD "Xaman" that has disc rot. It's a shame because that one is long out of print!
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