Why not field-test all motorcycle exhaust systems or, relay on in use vehicle pass-by testing?
Although states are preempted by section 4905e(1) of NCA from enforcing their own noise emissions limits (maximum noise levels) on manufacturers of regulated motorcycles and exhaust systems unless identical to the federal standard, they are free to establish their own noise emissions standards for competition use motorcycles and loud aftermarket exhaust systems. This is because the EPA has no noise emissions standards for these products; only labeling to show intent. The only easily applicable testing procedure police could use is the stationary measurement type like the SAE J1287. Unlike the EPA’s test (j331a) this test does not measure the in-use noise levels encountered while the vehicle is moving, under heavy load and large throttle openings. The J1287 test is part-throttle, no load, and has a very poor correlation to real world, in-use conditions as commented on by the EPA “the simple stationary tests usually offer such poor correlation that they would seem to be highly ineffectiv
