The problems with noise regulations for cars

Cars have always and to a certain extent will always produce noise. Usually it's a combination of sounds coming from the engine, the exhaust, the wheels and the air passing the car. Due to the fact that more and more cars were driving around, the authorities created laws, measurement approaches and maximum noise level thresholds to get the problem under control. Over time these laws and maximum noise levels were made stricter. The "machine" to create and update laws though is quite slow and inflexible, as for example in the EU consensus and agreement needs to be reached before a new or updated law can be published. Because of this technology advances much faster and the car manufacturers (and tuning companies) invent new technical approaches to deliver what (some of) their customers want to buy - a well sounding and not too quiet car. If you look at the latest Aston Martins, Maseratis, Porsches or Ferraris, they all come with a sophisticated exhaust system that uses different channels conrolled by flaps and gates to emit the noise, depending on the driving condition or a (sport) switch in the car. When the car is homologated and measured based the rules stipulated through the law these cars of course emit the minimum noise level allowed and nobody would hit the special (sports) switch in the car. As a result these cars are substantially noisier than some cars in the 80ies or 90ies that were ruled out by the laws at that time. Thanks to the fact that complex exhaust systems are expensive this hasn't become a major problem, but it illustrates the problems the legislation suffers from when trying to lay out rules for technology. Where it becomes very irritating is when you try to road register older cars (for example after having imported them from one country to another) and therefore have to comply with the rules from the date when the car was manufacturer (or registered the first time).
As a petrol head I love the noise that well engineered cars produce. I think that the new Maserati Grandsport sounds terrific and would really be disappointed if an Aston Martin DB9 couldn't show off its well orchestrated V12 noise. And I would consider the sound output of a Ferrari 250 GTO, Jaguary D Type or Porsche Carrera 6 almost as music. But I must also admit that life would be hell in cities if all vehicles produced the noise level of these mentioned machines and therefore understand the need to regulate noise emission very well. But ...