I'm trying to remember how loud the Nashville Motor Speedway is. When I was a wee kid, we used to go to Nascar races there. That Speedway/Fairgrounds is located in an area much like Franklinton - mixed commercial, with pockets of houses tucked in all around. I would actually say that Cooper Stadium has more of a land barrier around it, with the cemetaries and highway right there than in Nashville.
Anyway - what I remember is that it was PAINFULLY loud inside the stands, but that as soon as we cleared them, and got to the midway, the racing was a drone in the background.
It would be interesting to see what it's like now, as I believe they are racing similar style cars as what is proposed @ Cooper.
I think sinking the track makes a huge difference - and I think the walls could be much better looking than a weedy parking lot or run-down building. I have no idea what the plan is, but I'm envisioning something like the sound barriers that run down 71S, before 270 - the ones that are sculpted with trees and such.