Aluminium

Jack White has stated in the interview with the five-year-old kid that this song is imitating the sound robots make. Of course, this cannot be taken too seriously, but with Jack's obsession with truth and children, I don't think he would lie to the kid, even to humor him. We also know that Jack hates cars.

So, the "aaaahs" are purposely ugly and harsh on the ears, just as technology can be ugly and harsh. Perhaps it is another desperate White Stripes song urging us to focus on what is natural, real, and important.