The gnashing and grinding of the city

[blwings]

The car is near the Institute. She knows this without looking up because the sounds of the city have finally fallen away, as if Lila Mae and her driver had discovered the one true valley. The gnashing and grinding of the city, the keen laughter that follows a fresh kill.

This is from The Intuitionist by Colson Whitehead. I wonder what "the gnashing and grinding of the city" means here? Does it refer to the sounds of the city?

 

[emsr2d2]

Yes.

 

[Tdol]

Unpleasant ones.