Running power and signal cables

I had my amp installed at a local shop about 3 weeks ago and noticed a little alternator whine. Well, yesterday I started investigating the problem myself, because they had no idea what could be causing it. I noticed that they ran all of the cables down the same side of the car. I took the signal cable and turn on lead and moved it to the other side of the car and this completely fixed the problem. My question is: isn't it common knowledge not to run the power and signal cables on the same side of the car? I've never read any amp tutorials or anything that have not specifically mentioned running them on different sides.

Yes, that is common knowledge. Sounds like the car audio shop is just lazy and does not care about the quality of there installs or customer service or they are just plain idiots. Obviously, you should probably take your business else where the next time around. Shops like that just kill our industry and that is why alot of consumers buy off the internet now a days. It is a shame. Jazzy

Well, the only reason I plan on going there now is to buy products, not get work done. Hopefully, I'll be doing my own installs from now on.