I remember finding a link on this site (years ago) to California OHV noise test data for dirtbikes. I can't find the data now. Does anyone know where that data is located?
Here's a link to a more modern thread with some of the same procedures detailed. Ultimately the link I think you want to the actual data is provided by Okie in this thread.
Just a teeny tip of what's hiding in DRN- I could easily create a whole forum just around sound/regulations/pipes and performance. Some good stuff hiding in those stacks.