I have heard of some guys who have dumped before the axle, they angle the dumps at around 45 degrees so the pipe is not shooting directly at the ground and then echoing back up. Said it helped alot

 

dont do it, its loud as hell but it does get old quick. i like the sound just not the volume. i was too cheap to put pipes on it.

 

i already did it...it sounds awesome...barely any drone at all check out the video i made in the multimedia section to hear it...but the sound sucks on the video cause i made it with my digital camera which isnt really meant for filming