It is what noted in the Truck technical papers which is a part of road licence.
The noise measurement ist outside not in the Cab
Our Chevy have no insulation and about 6o Miles you can talk and understand each other in the Cab
Also a way to restrict speed.
There is like all in Germany a long list of rules to follow
I attached a description and used a translator for it... hope it is useful to read
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
Also on German language is the reading of that tiring
Scroll down to the end, there a 3 pics in the PDF which schon the measurement points
Police doesnt make a DIN Measurement
They use some points of that procedere and if this shown a big difference...
They cant take you out for 1-2 db difference
If you be detected than you go to a technical testing and DIN Measurement, which you have of course to pay yourself.
Can you bring the proove it is measured like the papers shown all will be payed by goverment
Usually they pick tuned Motorbikes and Sportcars out with aftermarket loud exhaust systems