When I went to my first American Le Mans race a few weeks back, I was blown away by two things. The first was how incredibly quiet the Audi TDIs are. While I was standing at the sidelines with other spectators at Road America, everyone was talking about how those big diesel V10s are barely audible. They actually sound more like a cartoon spaceship than race cars, and it's really, really impressive. The other thing that blew me away? How mind-numbingly loud the GT1 Corvettes are. Oh. My. God. I spent years writing about rock music, and I'm probably half deaf, but the 'Vettes are still loud enough to make me wince when they pass. Every time the drivers let off the throttle, it sounds like a bunch of M-80s fighting in a bag, and it's beautiful. To see how the two machines compare noise-wise, check out the clip below. You might have to turn the volume up to catch the TDI, but you could probably hear the 'Vettes even with the sound set on mute. Enjoy.