I ran my ac line in the same track as my dc line from front to rear of the bus. when i play my stereo in the rear i get a whisker of hum that i can only hear when the music volume is so low i can barely hear music.
AC does induce noise into dc lines. Yes. If you are a sound engineer then by all means run em apart. Also i have these wires run along the floor, if ever there is a problem it will not be a hassle to change. If i were to run behind a wall with insulation.... i would probably run em a few inches apart.
Good question, and good luck!