Originally Posted by Jon [in CT]
I think you should take measurements at the distances and angles specified by CA regs (which, so far, have not been presented here).
Throw a brother a bone here Jon!
You are the .pdf/regulation Guru, hook a brother up if you know/can find the real info!
From my limited research, I would need a sound level meter complying with ANS S1.4-1971 (mine isn't and the real things run ~$300) and would have to comply with SAEJ1169 Testing Procedures:
And the Engine RPM must be held steady at 75% of rated peak horsepower RPM. Given the latter figure is 6,000 RPM for the US spec WRX/STI, the test speed is 4,500 RPM for these vehicles.
This is all too much of a pain for me to think of doing, so sorry California Scooby owners.