[HawgRyder]

A couple of rules of thumb so to speak:
More turns in the headers = lower tone.
Longer pipes = lower rpm torque.
Heavier metal in the pipes and mufflers = lower sound.
When the exhaust pulses are forced to cross each other it lowers the over-all sound out.
If you apply sound absorbing packing around perforated pipes it will diminish the sound levels...and possibly lower the tone a little too.
How's that for a few rules?
Bob