OK, here’s something nobody is talking about:
ALL the automakers, foreign and domestic, use “Defeat devices” to meet federal, state, and local NOISE laws.
Even though the federal motor vehicle noise law (40CFR 205) comes under the EPA, the arm of the EPA charged with enforcing that law was defunded decades ago, and compliance has not been enforced since about the early 1980s.
That’s how noisy diesel trucks, from pickups to Peterbilts, can be sold as they are.
States and cities have noise laws on the books but lack the expertise to measure compliance.
Ask me how I know...
How do you know? ;)
They are called mufflers. And customers like them because they make the ride quieter, not because government mandates them. The market would demand a quiet ride regardless of whatever laws there were. Its why car cabins are also better insulated to keep outside noise out.