I had the pleasure in 1972/3 of meeting a gentleman at Santa Barbara Int'l Airport who had a p-38. There were several other 'warbirds' at that feild. When one of those others fired up you could hear it over ANYTHING else running,from anywhere on field,even at idle they were unmistakable , they included a couple P-51's, AT-6 and couple others lost to mists of time...
But when that P-38 coughed and lite it purred..P-51's have a rather short exhaust stack..few inches..no muffler, baby.The 38 runs exhaust back over engine to turbo-charger..was sweet sound.
JGroth