There is a difference between drone and normal exhaust sound. What I've discovered is some folks have differing opinions on what the difference is. The only common thing I've noticed is the younger the individual is the more likely they will say the sound you hear is normal exhaust sound, and the older folks will say what you are hearing is drone.
2011 Le Mans Blue M3// Black extended Novillo w/ Blue Grey Aluminum trim/DCT/ZTP/ZCW/ZPP/ZCP Premium Sound ///Akrapovic Evolution Exhaust
2012 Le Mans Blue 135i M Pkg DCT
2013 Ford F150 FX4 Supercrew