I had a car once that really did sound like an airplane: a Mitsubishi Tredia with a 2.0 SOHC "silent shaft" engine. The silent shafts were these rotating counterweights that cancelled out the main frequency of engine vibration. They really worked. The sound that was left behind was thin and high and reminiscent of nothing so much as a jet turbine.
Then there was an oil failure that wrecked the head, and when I put the engine back together I didn't bother to reactivate one of the two silent shafts. After that it sounded like a regular 4-cyl engine.
The thing always had rich/lean trouble too... it was a lemon, but I got it for like half of market price.
