Devon and Cornwall police recently bought seven decibel (dB) meters which they are using to measure the sound levels of vehicle exhausts.
They have already started issuing FPN’s and fines for ‘Overly Loud’ exhausts.
BBC - Sound meters tackle noisy drivers
The police say that trained officers will be using the equipment in areas such as The Hoe in Plymouth which is regarded as a ‘trouble spot’ for drivers of cars with modified exhausts.
A police spokesman claimed that “During the first trial in Newton Abbot, Devon, a driver was fined £30 when his car exhaust was making more than three times the acceptable level of noise”.
The report later says that “Vehicle noise levels should be between 82 and 89 decibels”, although whether this was the ‘Legal’ level or just the ‘Acceptable’ one is open to discussion..
In regard to the motorist issued with the FPN, the report say that his vehicle was found to be putting out 93dB.
The maximum permissible level to pass the BIVA test is 98dB, which is down from the SVA limit of 101dB
ISO 5103
There is nothing in the report that show what testing procedure the police are using and officers are trained in the ISO 5103 process, which is the internationally recognised procedure for conducting stationary noise tests on motor vehicles and details, amongst other things, microphone placement and the engine rev range that should be used for such tests.
A recent Dft document assessed the various methods of noise testing for vehicles and details some of the problematic issues involved with roadside tests involving inexperienced testers.
Vehicle Noise Test Procedures
Devon & Cornwall Constabulary’s response
We contacted Devon and Cornwall police with these concerns and received the following response for Sgt Keenan of the Traffic Division.
“We are looking at two different offences. Modifying a vehicles exhaust beyond the ‘standard’ EU limits and Producing excessive noise.
For this we have purchased 7 Cat 1 testers which are set up and used in accordance with ISO 5103 testing procedures.
We take a number of ambient readings and readings taken at different engine rpm’s from a fixed distance and angle to the rear of the vehicle to get an average Db reading.
The figure we use in 82-89 dB, this is the EU Limit for Type approval, even though there is no actual legal dB limit on road vehicles.
89dB is a large 4×4 at full throttle.
We will consider prosecution at 90dB and so far, in testing we have had one vehicle at 103dB and one where we had to abort the test due to complaints about the noise level while the test was being conducted.”
We asked about the position with an SVA’d vehicle, where the threshold for a failure is 101dB and were told that and said that “If you produced an SVA certificate we would not prosecute if the level were over 90dB”.
“If you fail the noise check but claim that you did not modify the exhaust, in other words the exhaust is how it was when the vehicle was purchased, we will not prosecute based on modifying the exhaust, but will use the Excessive noise legislation instead.
This is an area where the ‘Tone’ of the exhaust is as important as the noise level and is at the discretion of the officer and can be a reason for the vehicle to be tested.”
Sgt Keenan also said that, if a vehicle was reported as too loud, but when tested was under the level they would consider showing the readings to the complainant as a way of educating the public in terms of what is and is not an ‘illegal’ exhaust system. Also, the readings are considered to be guidelines to assist in court cases but are not a basis for court action in their own right.
Some interesting things come out of the response.
D&C constabulary are taking a firm, but sensible approach to this issue, in that they are conducting ‘Proper’ tests as opposed to just ‘Sticking a probe in the exhaust’ and they are aware that there are certain vehicles that will fail the roadside checks even though they have passed elsewhere.
They also hope to be able to use this testing to ‘educate’ people on the subject of exhaust noise.