Where does your figure of double come from? In Australia the legal limit is 100db measured 1m away. 110 db is already 3x the sound level, and measured 15 times the distance away, and falloff is function distance squared.
Concerning uncorrelated signals like noise you need 6 dB(A) for double energy in an objective way. In a subjective way concerning the psychoacoustic detection you need 10 dB(A) for double noise. That´s the difference.
If you mean the FIA standard noise regulations by the "legal limit" it´s actually measured 100 dB(A) at 4500 rpm 0,5 m away in an angle of 45 degrees from the exhaust. But it´s the limit only for offroad and some saloon racing.
But that´s not the method used any more at eg Hockenheim circuit or at 24 h of Le Mans because it´s inappropriate. Look at the directives from the german federation DMSB (it´s in german, but the graphics should speak for itself):
http://www.dmsb.de/downloads/2668/Dr.E. ... fahren.pdf
Don´t know how it is in Aussieland, but in the European Union, a car race is not permissible unless official approval has been obtained. And the laws are requiring noise reduction. Thus you have to consider the Council Directive 85/337/EWG from 27th of June 1985. (see page 2 of the DMSB paper). It states: The louder, the fewer days of race action is allowed (page 7). The measuring of the proximity stationary noise level as mentioned above (see graphics in page 14 and 15) was replaced by the measuring technique from a certain distance (from the grandstands or surroundings) when the car is in motion at full throttle and at high revs. So it´s the sound power of a source, not the noise pressure level. So the car HAS about 130 d(BA) on track at Le Mans, but 110 dB(A) 15 m away in a psychoacoustic manner as it is allowed because of the falloff. If it would have 150 dB(A) on track, it would be too loud.
Currently, there is an EU programme on the run further reducing car noise, which via United Nations should be established worldwide. So, altogether there is necessity to reduce car noise, otherwise race tracks will get into legal trouble.
having never been to a grand prix i cant comment for that, but i have been to the red bull home run...
And I guess you never attended a V6 turbo engine run in the year 2014. So that´s the reason why the whole "sound discussion" is completely useless.