Weird, Never thought of this as a noise issue.
I did think this was an emissions issue. Sucking the fun out of driving with every new regulation.
Why Building a Modern Manual-Transmission Car Is So Complicated
Mar 1, 2024
The transmission itself might be basic, but building a manual-transmission car is extremely complex. And I’m not just talking about making the business case for a niche option sold only to true believers (in America, at least). Frankly, plugging a manual transmission into a modern car requires some weird engineering.
Drive-by noise regulations affect gear-ratio selection, for example. As a hypothetical, if a car has to be below a certain noise threshold at 35 mph, you can simply program the car to use a higher gear. In a manual car, you obviously can’t.
"The ECU is in the driver’s seat," says Michael Rosler, head of Porsche’s 911 product line.
So you’ve got to pick gear ratios that keep the engine at lower rpm for a given speed to satisfy those noise requirements.
Noise emissions are a problem, as are particle emissions. An SAE paper published last year by researchers at France’s Nantes University and Renault notes that in manual transmission cars, driver behavior has a huge effect on emissions performance.
https://www.motor1.com/features/7106...-cars-is-hard/