Maybe that's it? It just kind of whistles as it goes past - it's kind of exciting, in a stealth bomber kind of way.....
I saw the initial shakedown test video from Sebring. It looks like as well as looking good, and sounding deathly silent, that it also goes like absolute stink! Cornering speed looked out of this world! I guess this is confirmed by the laptimes - I think I remember Rick telling me that it had set a lap time just under 10 seconds per lap quicker than the fastest Peugeot over PQ? At that rate, they'll be able to run for 12 hours, and take the rest of the race sat in the pit lane!!