Audio Systems: Defective CDRs, playback performance, cdr quality

Question
I have been storing CDRs (containing music which had duplicated onto them) on the floor and I discovered some audio defects which I don't believe were there when they were first produced about a year ago. (I double checked the masters and they are clean.) The CDRs are situated about 15" from a pair of AKG mikes, and also near some electrical wiring, a similar distance. Can those items have affected the CDRs?

Answer
Defects can be from poor quality CDRs as they will often deteriorate with time.  Also, it often depends on the combination of the CDR quality and the recording machine/instrument being used.

It may well be, also, that the cd player you are using is not in perfect alignment and is reading errors that some other machine would not detect.

There are many variables and so many folks such as yourself have found variable results - especially with questionable disc quality and recording machine.  There is a site that has many answers to questions about CDR issues.  Try looking through it for some ideas:

http://www.videohelp.com/search.php?cx=partner-pub-7958603558688719%3A6824369548

You should try the discs exhibiting audio defects (we call them dropouts) on other cd players to see if you find a variation of performances. If the dropouts occur in exactly the same position on every player then the defect could very well be on the disc itself.  

Hold the disc up so that light reflects off the surface and examine for color changes or irregular surfaces.  Sometimes the discs deteriorate of their own because the surface coatings were not perfect at the factory, etc.  

Thus, your job now, as I see it, is to determine if the problem is contamination or imperfections on the disc or variations of playback performance or compatibility or little of both.

But, the electric and magnetic fields you refer to are of no consequence in my opinion. I doubt very much if they had any effect on this matter.

Hope this helps.

PS: There are great differences from cd player to cd player of their capability to read through errors on a cd.  The detection and correction algorithms used and their sensitivity to optical alignment of the laser diode is a very large contributor to good vs bad performance in cd players.