"Drone" is a constant harmonic vibration/reverberation heard in the cab of the truck usually occuring above higher RPM's/speeds from either the intake, exhaust, or some type of mechanical vibration....eg. knobby tires, transmission hum, bad wheel bearings etc. Some people love the sound made from high performance mods...other people find it rather annoying.

 

4 ways to get rid of drone:

buy a muffler with a 'Helmholtz Resonator' built in

avoid a length of tailpipe from muffler outlet to exhaust tip
that is in the 55 to 75 inch length range

study 'sound wave filter design in ducts and pipes'
at the GM Institute for teaching automotive engineering at home,

http://www.gmi.edu/~drussell/GMI-Acoustics/Filters.html

and place resonators at exactly the right spots to kill both MDS 4 cyl and full 8 cyl drone in the 1500 to 2500 rpm part throttle range

go to work at Bose and learn the secrets of 'anti-noise electronic sound reduction' and put speakers near your exhaust pipe tip

 

...ooorrr get a longer muffler that can absorb longer wavelengths = lower frequencies

 

Drone sounds like a low hum/vibration that rattles your teeth loose. It sounds like a blown subwoofer and the sound emanates from everywhere. It can cause intense headaches and nausea in some people. It usually occurs at 1500-2000 RPMs at highway speeds with a muffler that doesn't cancel out these low frequencies.
There is nothing good about exhaust drone.

 

mystro, what sizze muffler are you using now? I think you've sold me on going longer, but want an idea of how long I should be going.

 

I think the body length is 24".