Now you take one of my OS 4 cylinder 4 Cycles in a Cub or my Five cylinder OS FF300 in a Fleet Biplane and you get a more realistic sound than a scrreaming 2 cycle or gasoline engine sounds like a Rolls merlin. By the way someone awile back mentioned a Packard Merlin. Now THAT would be a rare engine. Rolls Merlin or Rolls Griffin I will believe but a Rolls packard?? Nope.

Oh and turbines sound like a small vacuum cleaner.