Yamaha TRX850 Enthusiasts Forum

Here is a great explanation on resonance and will give you a visual perspective on how exhaust tuning and pulse works to give you gains.
This also relates to tuning of your airbox and timing the resonance to the valve overlap.
When you see how the flames interact with music remember frequency is a number of revolutions just like a motor.
You will see at certain frequencies the gains in the flames so you have the length correct so that gain happens within your combustion chamber, more heat = more power.
Enjoy....
https://www.youtube.com/watch?v=dihQuwrf9yQ

Pretty cool. I remember covering this in high school physics. For any given vessel you can work out where the nodes will be for any given musical note pretty easy. Can find the formulas in any high school physics book. I dont think it will be much use to you trying to design or modify an exhaust so much though as there is so much more going on with gas speeds, pulses and temps on top of the acoustic stuff, but it does definitely illustrate the importance of all the R&D the manufacturers put into exhaust and intake design.
I like the bit at the end where he plays music through it. Reminds me a bit of the graphic equaliser on an 80's stereo system lol.

Here's why body deadener is a good idea in your car;
https://www.youtube.com/watch?v=wvJAgrUBF4w

Love this sort of stuff