It does not generate black smoke and is not the cause of global warming but it is still a source of pollution. Even if only a single truck is considered, noise is a nuisance with many sources.
Trucks are quieter and quieter
On a tractor-trailer rig, noise emissions can be attributed to three factors: engine operation, aerodynamic turbulences and tyrecontact with the road. Over the years, in the same way as for gas and particle emissions, regulations have become stricter to reduce noise pollution from engines. The authorised threshold has been reduced by 11dB in thirty five years. This number seems low as long as it is not converted into noise pressure or the “amount of noise perceived by the human ear”: 11 dB is the equivalent of almost twelve times less noise.
Aerodynamic issues aremore difficult to address, mainly due to the various types of trailers which must first satisfy specifications on their use. Yet, tractor vehicle manufacturers are working to reduce the drag coefficient since it also brings a reduction in fuel consumption.
Low noise tyres, the best solution
Last, but not least, rolling noise, which again, has several sources. It is caused by the vibrations of the tyre itself due to road irregularities, by a pressure phenomenon and the suction of air when the tyre “bounces” on the road, by a hammering noise generated by the tyre due to the gap between tread blocks and by the reflection of noise on the road. Indeed, sound waves are only partially absorbed by the road. A solution to reduce rolling noise therefore consists in laying noise-absorbing road surfaces. However, this represents a significant cost for a surface that is less durable than a traditional road surface. Therefore, improving tyres seems less expensive and easier to implement. Given that European tyre labelling includes a criterion for external rolling noise, tyre manufacturers are all the more motivated to work on reducing noise.However, according to studies, this criterion is less important for purchasers, way behind rolling resistance and wet grip…