My living room has a 5.1 Dolby digital system; the audio cables for the three front speakers run through the walls for about 13 metres (about 42 feet) in a corrugated pipe with a diameter of 2.3 cm (a bit less than an inch).
A few days ago one of the speakers stopped working, after several years without problems. I traced the problem to one of the cables; I pulled all of them from the pipe and I was surprised to see that they seemed corroded in several points.
The insulation had failed - apparently scraped? - and the copper had corroded, even if I thought that copper oxide was green; the exposed parts showed a whitish dust instead.
The pipe runs indoor, it was never exposed to water and I doubt there are tiny 1" rodents in my place. The house is six years old.
Now I'm in the process of pulling a new set of wires through the corrugated pipe; it's the one with the green probe sticking out of it in the picture. I don't think it's relevant but it also has a perfectly working cat5 cable in it.
I'd like to know what happened to the old wires and how to prevent this in the future.