One thing I noticed at the Chino airshows, is that the P38 and P47 sound so much different than every other warbird. Its almost a muffled sound as compared to the sharp racket of a Hellcat, P40, P51 or Spitfire
I think its due to the exhaust ducting is designed to blow into turbochargers and must be "collected" from all the cylinders into one big duct.