Firstly, think of the woodwind section in an orchestra and what do you realise? You realise that the sound coming out of the an oboe, flute or other doohickey is the result of resonance determined by varying the length of the air passage inside it. So resonance is the KEY to the note.
Reasonace can also be varied by volume and that's why different instruments produce a low or high tone base.
Your exhaust system is like a woodwind instrument but I don't expect you to play Jingle Bells on it like like formula 1 teams. So bear in mind that big bore systems will produce lower notes (even if they are configured to attenuate noise to the same degree as smaller bore systems) Naturally, the opposite is true that smaller bores produce a higher pitch (note) pipe reasonace.
What's my point?
When you start considering what sort of exhaust sytem you want on your car and apart from legal compliance issues , for Pete's sakes don't start with daydreaming about this brand or that brand of muffler. Think through the ENTIRE system for efficiency, fit, servicability,effective life, nature of materials, ground clearance and somewhere last on the list if you don't run out of paper, the note.
The exhaust note is the consequence of fulfilling all the other functional criteria and should be appreciated for its own qualities whatever that is as opposed to having a great note at the detriment to everything else.
Might seem like an obvious thing but try telling that to some rice burner dickhead driving around in a shopping cart hatch with a vacuum cleaner sized stainless steel muffler with a pretend big bore system good enough to serve a Mack truck but not enough power to pull the skin off stale milk and complete the picture as a total WANKER!
Don't go there...
Hey check out Barry's system for his pick up truck. Now Barry does play Jingle Bells actually 'cause he carries the organ in the back tray and he needs all the pipes for the organ. Got a few clues our Bazza he has... 
