Legal limit of exhaust


Member +
It would be very helpful if someone could post some info regarding the way decibels are recorded to test the amount of noise a car exhaust makes in the UK.

What i am interested to know is the methodology?

For example in Japan you have to hold the sound meter 50cm away from the back box at an angle of 45 degrees.
And legal limit seems to be 96 dbs over there.

Many thanks.


Member + Comps - Vehicles.pdf

see page 150

these are the limits for motorsport and how they are measured in the uk. like japan it is taken at 45 degrees to the outlet. it is worth noting the different Db readings at 0.5m and 2.0m. whether the test is conducted at 0.5 or 2.0m is up to the scrutineer carrying out the test.

other requirements for example are carrying out the test away from walls or solid objects where the sound bounce off and affect the reading. engaging the clutch and whether the car is up to temp or not will also affect the reading.

hope this is of some use, any questions, fire me a pm.


Member +
This is altogether interesting.

Many thanks for posting this pdf.


While this is for motorsport, how about normal driving?