SAE J1169 Light Vehicle Noise Measurement and superseded by J1492. California uses these when there are noise complaints on a specific vehicle.

When I was young (1980's), I ran Hush Thrush bullets connected to the collector. Man - was that loud. I got pulled over plenty of times. In the 90's, I switched to a H-pipe with FlowMaster original 40's. Those were better but still pretty loud. Then I had kids (2000's) and the car was just too loud so I switched to an X-pipe and Walker UltraFlows. Now, my hearing is in decline so the UltraFlows are too quiet. I'm going back to the Original 40's ... they were free ... I still had them stashed in the garage parts room (attic). I have a friend who runs around with FlowMaster Super 10's ... he's REALLY loud.

I want to do the J1169 test with the UltraFlows and then test again with the Original 40's just to see where the dBA numbers are at and if I'm close to the threshold for getting in trouble. It would be nice to have already run the tests and know where you stand BEFORE the cop pulls you over to talk to you about your exhaust noise problem.