Dolby Surround Sound CDs - Question

What can you tell me about Dolby Surround Sound CDs and what causes the "surround", as in different audio information in four channels?

Is it all phasing, or some other type of decoding?  I have one of those beasts with some really nice music on it but some idiot overlayed beach sounds, etc. that I'd like to remove.  Do you think it might be possible? 

How does one go about it?  I've never tried but seem to remember readiing on an oldie board that others have been successful in such endeavors.

Thank you.

Dolby Surround has evolved over the years because DSP is now so much more powerful than the old analog decoding hardware, such that ProLogic IIa gives 5.1 or more channels from a matrixed 2-channel carrier.  But I chuckle when I see so many guys trying to re-encode their CD collection to 5.1 by creating redundant channels and extracting this and that, because the result is so vastly inferior to what ProLogic has risen to in realtime processing.  Ain't no way it's better than discrete 5.1, though.  Sits kinda in the middle.

OK, having said that, you're right: it's all done by phase.  So you can try to remove the beach sounds by using the Center Channel Extractor in AA2 or 3, which will leave you with a largely mono end result if it's do-able at all.  Of course, the CCE can extract far more than the center, so play around with the settings.  Of course, the newer spectral phase display in Edit View is pretty spectacular for this kind of work, too.