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> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx] On Behalf Of Steven C. Barr(x)
> Sent: Sunday, October 15, 2006 5:16 PM
> To: ARSCLIST@xxxxxxxxxxxxxxxx
> Subject: Re: [ARSCLIST] MP3
> ----- Original Message -----
> From: "Mike Richter" <mrichter@xxxxxxx>
> > Steven C. Barr(x) wrote:
> >
> > > Side thought...since all analog reproduction so far relies upon
> > > mechanical contact with the recording, does not that mean that
> > > ANY playing of an analog recording would involve some measurable
> > > degredation of the object (recording) being played?
> >
> > Certainly, there is some deformation. Probably there is degradation.
> > Possibly the change may be detectable. Detection itself means some form
> > of measurement which means some sort of playing which implies
> > deformation, probably degradation ...
> >
> > As for optical reading (laser or otherwise), there will be quantum
> > effects at least, though admittedly the deformation and potential
> > degradation will be exceedingly slight.
> >
> I think I posted a while back to the effect that the laser beams used
> to play optical discs could, at least in theory, knock a few billion
> molecules from their places...but was told that wasn't possible
> because the actual information-bearing surface is protected by a
> layer of transparent plastic.
> Is this so?
> Steven C. Barr

I believe that I replied to this earlier. Molecular "ejection", or most
degradation mechanisms, have an energy threshold, below which incident
radiation has no effect. IR and red laser quanta have low energies, and
single photons would have no effect. Of course, intense beams can locally
heat, which is the means of recording to CD-R and CD-RW discs.

Media Sciences, Inc. 

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