The sound in the game is great. I am pretty sure they use the same voice actors from the original Disney Pixar movie, but don't hold me to it. They sound enough alike that it doesn't matter either way. The racing sounds are well done, and the music isn't annoying like in some games that are marketed at kids. I did get a little sick of the cars that I passed talking to me. "How ya doin'?" and "You hit me!" got so obnoxious after a while. If they wanted to go "Like, omg, you are so fast!", I wouldn't have minded that overly much.
Oddly enough, there is no background music for when you explore Radiator Springs. I don't know if they just got lazy, forgot about it, or thought it wasn't needed; but I have to say... I missed the background noise. You still get race and car noises, and the car characters still talk to you, just no fun music.