Editor’s ViewComing to Grips with Traffic <strong>Noise</strong>Traffic noise is one of the most uniqueenvironmental noises affronting modernman. Although it can be high in level in somecases—such as next to a busy freeway—its realuniqueness stems not so much from the level of noise,but rather its omnipresence. Adding to its uniquenessis often the dispersion of authority or responsibility,confounding efforts to do much about it. Finally, likeno other type of transportation noise, motor vehiclenoise enters that realm of individual versus collectiverights as some operators insist on making even louder“sounds” with their vehicle. It is no wonder that theUnited States as well as probably other countriesof the world have a difficult time with developing arationale plan to produce real improvement.In the modern environment, motor vehicle noise isvirtually inescapable. This is largely due to the greatfreedom in mobility that motor vehicles provide.They can travel in great packs producing highlevels due simply to their numbers such as alongour freeways, or singly where their level may not behigh, but stands out relative to low background noiselevels. Even away from identifiable packs of vehicleson roadways, the background noise frequently is setby the presence of many, many of them operating atvarying distances away. Just based on this exposuremodel, it is clear that there is no single noise control“fix” that will address all situations.But there are fixes available and if they all could beapplied in a rational manner, real improvement couldbe made. Many of these can be found in the FinalReport by the I-INCE Working Party on the Effectof Regulations on Road Vehicle <strong>Noise</strong> as publishedin the September 2001 issue of this magazine. Onepositive step is the changes taking place in the ISO362 passby noise test procedure, which will sooninclude tire noise dominated cruise conditions aspart of the reported emission level. This will atleast bring lower speed emission levels more in linewith actual lower speed operating conditions. Otherfixes on the source side include the use of quietpavements to reduce tire/road noise particularly formotorways and freeways. Depending the on theinitial pavement, reductions of 5 to 10 dB can beachieved by pavement selection. Also, on the sourceside, is the issue of quieter tires. Although moretypical passenger car tires may show only a rangein A-weighted level of a few dB, when “off-road”4x4 tires are included, this light vehicle range canbecome significant. For truck tires, a spread of morethan 10 dB exists between those used on the steeringand trailer axles and some of those used on thedrive axles. Then there is the whole issue of poorlymaintained or intentionally modified cars and trucks.As a result, the range in level for highway passbyconditions for light vehicles is typically 8 dB and 7dB for trucks. On the path side of the equation, ofcourse, there is the ever-popular sound wall that mayyield a 8 to 15 dB reduction, at least close by.Although there is a good list of potential fixes, theproblem comes when you look at who is responsiblefor what and who is there to bring it all together.For new vehicle regulation, a federal governmentalauthority is typically responsible for setting theallowable noise level and manufacturers for theimplementation. For this to be effective, the levelsshould be rational and relate to real world noiseexposure. But as the I-INCE Working Party found,these may not be effective if done in a vacuum. Thatis, the low emission levels may be negated by the firstafter-market tire purchase or by transverse texturingof local highway surfaces. For trucks, tire noise isfurther complicated because truck manufacturers donot specify the tire type, but instead it is left to thepurchaser. In the US, pavement type is a state or localhighway agency’s decision, and its use as a noiseabatement strategy is not yet supported by the FederalHighway Administration. Federal support goes onlyto the construction of sound walls and only then whenat least a 5 dB reduction can be achieved. The finalelement is in-use control and enforcement. In theU.S., this is unpopular with the taxpayers who fundthe enforcement and unpopular with those who wantto get the “right sound” from their exhaust system orlower back-pressure for their “big-rig” truck.Can we get a grip on traffic noise? Perhaps it canbe if we use three or four hands and have a head tocoordinate them.NNIPaul DonavanPan-American<strong>News</strong> Editor2005 December www.inceusa.org • www.noisenewsinternational.net • www.i-ince.org113