[joedoh]

I have had drone on two trucks with pipes out the back. I have had no drone on trucks with axle dumps. When you add length to pipes (or shorten them) you are inherently changing the resonant frequency. See my comment above on cutting the length of the pipe and its effect on the frequency. I think a straight through muffler acts like a continuous piece of pipe for the standing wave, and a chambered muffler does not, but that is just a theory.

what got me interested in it was hearing a (then) new 350z from just behind and beside it as it ran through the gears, fantastic sound! I started researching the design and found an article discussing how Nissan used Yamaha (the piano division) to find the right placement for silencers and mufflers and tune the sound, even choosing the resonant frequency and related harmonics to compliment the standing wave in the INTAKE. Apparently Lamborghini and Ferrari use the same technologies to tune their sport exhausts. I started learning abbout designing pipe organs of all things, and learned more about standing wave design. it was a rabbit hole for sure.