we want to penalize loud cars but we still don’t know how to do it

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Cities have waged a legal battle against noise pollution. And in that battle, cars are once again at the center of the debate. Noise radars are already in operation in some cities and their installation raises some legal issues.


What are they. Noise radars are a new control system to verify that sound sources do not exceed the maximum limits allowed. They are devices that have four microphones and 360º cameras, which allow the sound source to be detected, its trajectory and to photograph it if the maximum allowed limits have been exceeded.

The fine. The New York Police Department has brought these new noise radars back into the debate. From Road and Track they collect that a driver of a BMW M3 was sanctioned with an 875 dollar fine (770 euros) after a patrol picked up that the sound of his exhaust had exceeded the permitted limits. The solution: check the exhaust system at the place specified in the notification or pay the penalty.

Where. The New York City Council is not the only institution that has launched these noise radars. In Barcelona some tests have already been carried out, in order to collect information, although without the possibility of receiving a sanction. Switzerland or France also work with them and their use in cities will also allow bar terraces to be controlled, for example. In Spain, the DGT ensures that the installation of noise radars is not considered.

The 56dB. Sound is measured in decibels (dB) and its pressure increases logarithmically as the figure increases. For every six decibels the intensity of sound multiplies.. Thus, a sound of 75 decibels is almost 100 times more damaging than a sound of 56 decibels. These figures are important because, from 2021, all electric cars have to emit a minimum of 56 decibels, with the aim of alerting pedestrians to their position. The maximum allowed by an approved vehicle in Europe is 75 decibels.

Bmw M3 Competition Sedan M Xdrive 2022 1600 2d

source and measurement. With this sanction some questions are raised that the definitive installation of noise radars will have to explain. It must be borne in mind that in the cases indicated above we are always talking about the noise source, not the place of measurement. Thus, the maximum 75 decibels of a vehicle are less than a meter away and much less another ten meters beyond. The formula for this calculation is complex, since it involves intensity, frequency and wavelength, among other parameters.

Usually, the sound intensity drops drastically as the distance increases from the source. In fact, the sound detected at 200 meters will be a quarter of that recorded at 100 meters. Therefore, the position of the measurement control is decisive when it comes to obtaining the data and, therefore, processing the sanctions. A controller located in a patrol car next to a street will not be the same as on a pole 4 meters above the ground, as collected by the Directive 2002/49/EC of the European Parliament and of the Councilof June 25, 2002, on evaluation and management of environmental noise.

High resolution audio: myths and realities

Discriminate. This previous point is also key because the European Union sets the maximum noise allowed at 55 decibels during the day and 50 decibels at night. Of course, these figures have to be collected in the sound level meters that control the noise, which, as we can see, are lower figures than those indicated for any car.

It will also be interesting to see if these sound registration systems will establish maximum allowed times or fine anyone who exceeds the maximum number of decibels, even punctually. Also if in hospitals or schools, spaces of greater protection, they will have lower levels and, therefore, the passage of the noisiest vehicles will be endangered.

Cities have waged a legal battle against noise pollution. And in that battle, cars are once again at the center…

Cities have waged a legal battle against noise pollution. And in that battle, cars are once again at the center…

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