That's just my opinion anyway.
I respect your opinion and I respect every one who volunteers their time to keeps racing going I just want to try and shine a little light on how there might be some improvements.
The point of the sound limit is to limit overall noise travel to the neighbors, which is dependent on all the variables that apply to the current testing method.
That is an unachievable goal. You would need a different set of standards for each wind condition and temperature. During my previous life I have witnessed sound readings at the property line of a home 1/4 mile from a motocross track. The owner complained about the noise and had the county come for sound readings. On the day of the race the wind was blowing towards the track at about 5 KTS. The sound readings were so low that when a Corolla drove by on the paved road it read louder than the start and he had to wait for the next race to get an accurate reading. Later I was shown readings that showed when the wind was in the other direction the readings were almost 10 decibels higher. By the way, you are right about sound not being linear, a 10 db increase is generally considered as being twice as loud.
So many bikes, displacements, engine layouts, exhaust lengths/sizes/designs and muffler designs will not all give a linear sound level by RPM. It adds just as many, if not more, variables than it takes away.
You are right here to a degree. In my haste to find an example I just grabbed the first video I saw which is more for street bikes than race bikes. What if there was an example that all the major manufacturers agreed to for race bikes?
Fortunately there is and its contained here;
https://www.acu.org.uk/Uploaded/1/Documents/2020 handbook/06ACU-HANDBOOK2020-Road-Racing-Standing-Regulations.pdf
Just go to
AUTO CYCLE UNION HANDBOOK 2020 ROAD RACING 265
14.8 CONTROL OF EXHAUST SOUND LEVEL
Here is a screen grab of one of the major differences between this standard and SAE J2585.
View attachment 2488
As you can see there are different RPM for different configurations and displacements, even one for two strokes.
This standard was agreed to by all the major manufacturers in Europe, including aftermarket exhaust makers, and it is the basis for almost sound testing in racing there. Notice the RPM are higher and there is also different RPM for different configurations.
Also, that would require testing every single bike at the start of the day and wouldn't stop anyone from removing the insert they installed in the morning to pass sound. I would suggest that each bike is required to be tested once a year before it goes on track. A special inspection sticker would be issued After that the EMRA would monitor track side noise levels to see if anyone stands out as being excessively loud. If a bike is suspected to be loud a second static test would be run to see if there has been a change and justice would be dealt out accordingly.
Of course this is all based on whether there is correlation between static levels and track side levels. The manufacturers do based on their acceptance of the rules and in Britain there are many tracks that are close to towns or villages and they must meet more restrictive sound standards. These tracks have simple but effective strategies. I will give you two examples, Snetterton and Oulton Park.
Here is a copy of Snettertons noise restrictions.
http://www.snetterton.co.uk/media/975291/snnoisedocument_for_website_2010_rm.pdf
And here is a copy of Oulton Park noise categories.
https://www.oultonpark.co.uk/residents/news/noise-categories.aspx
For the basis of this lets compare Oulton Parks green limit with Snetterton.
As you can see there are two readings static and drive by. Static in Snetterton is 105 db and in Oulton Park is 102 db the drive by limits are 92 db and 89 db respectively. In each case they have determined that in order to achieve specific sound levels in surrounding areas they must achieve specific track side sound levels. They do that by setting static levels and monitoring compliance with track side testing.
I would like to point out that they use a 20 metre standard for track side. The exact specifications vary but the measuring device is at least three feet off the ground and 20 meters from the track. It is at a 90 degree angle from the track normally facing a straight such as the start finish straight and is situated so that it only points at on point one the track. In other words I think it would have to be in the infield. What the necessary track side noise level would be and what static level would be needed to achieve that would have to be figured out. Thats it. In short other people have faced this problem and found reliable ways to solve it to most peoples satisfaction. If I was racing and this was adopted I think I would take my iPhone to the static test and get a reading for my own benefit. That way I could double check if I made any big changes to the bike.