What creates "Drone"?

[alnukem]

I have a C3 Corvette & am going replace the "Block Hugger Headers" with long tubes. I am contemplating whether to go the normal 2.5" or bump up to 2.75" exhaust pipes & wonder about the drone, as these cars don't have all the creature comforts that our cars do. It is a 350 10:1 stick car with 3.70 gears & a small 268 solid roller cam. Thanks!