Does anyone have / know the exact wording for the laws regarding exhaust noise levels?

I know that you replacement exhaust is not allowed to be any louder than the factory fit item, however, is this compared at a particular rpm? over the whole rev range? at only the loudest point during the whole rev range?
Do the manufacturers have to declare a standard factory value which their exhausts produce and a percentage of this for acceptable variation?
How is the test carried out? I assume like at tracks it is at 45 degrees from the exhaust, but at what distance? at in what environment must the test be carried out?
If internal engine mods affect the output volume from the exhaust, despite the exhaust not being changed could there be a problem even if you are running the stock exhaust? and conversely if you are then running a non-stock exhaust that only produces above factory figures because of engine mods where do you stand?

How do grey imports get treated? are they rated against the same noise levels as their UK equivalents (if such models exist)? in which case many would fail despite running a stock exhaust system (less cats / silencers). Or are they simply rated against the SVA noise level, in which case you can run any exhaust system which still keeps the noise level below this?

BTTT

I don't think it matters, the stoopid green tree huggin nothing better to do whiney arsed meddling abused as a child no friends b*stards will find some irrelevant nonsense worthless pain in the ass bagosh*te ruling to cause you maximum aggro:rolleyes:

BOB(like the Murphy's, I'm not bitter).T[img]images/smilies/mad.gif[/img]

Dont think anyone cares, no one has taken any notice of mine and it's very loud, my neighbour runs a Ducati 996 with no baffles it drowns that out and the guy at the MOT station thought it sounds sweet.

Well that statement is wrong for a start!

You can use any non OEM system as long as it meets the maximum limits allowed and as long as it isnt physically modified once it leaves the exhaust manufaturers premises.

The noise limit for stage rallies usually matches the legal limit for road cars because all rally cars have to be road legal. If you meet these you will be road legal.

These limits are

100db(A) @ 0.5 metre distance and 45 degrees from the exhaust exit
88db(A) @ 2 metre distance and 45 degrees from the exhaust exit
76db(A) @ 8 metre from the centre of the car and off to one side at 90 degrees.

All these are measured at 4500rpm.

IIRC, the requirement for SVA tests is 101db(A) at 1m, 45 degrees, on hard surface, at 200mm hieght or centre line of exhaust (whichever is higher) at 2/3rds of maximum power revs. Can't guaranteee my memory, but that's just slighly more lenient than JF's numbers for rallying, so seems to all add up.

An exhaust does have to be pretty loud to excede those levels. At 5000rpm, 1m and 45º (done in a carpark, but with a calibrated hand-held meter), my bugeye with full APS system only gave 88.5dbs. (haven't checked it since up-pipe and ported headers, but subjectively it's no louder) OK, there are many noisier exhausts, but many "non enthusiasts" tell me mine is loud.