Urgent need for a quiet truck
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• It is technically feasible for manufacturers to meet a noise level limit of 86 dB(A) for the majority of trucks, given an appropriate lead-in period and, in the long term, reduce engine noise by about 10 dB(A) by radical redesign of the engine structure. These statements are made in a report published this week by the Road Research Laboratory. The report—LE 357, A Review of Road Traffic Noise—points out also that one of three areas in which research is urgently needed is "the development of a demonstration prototype of a quiet.heavy commercial vehicle".
In its 94 pages of text the report covers all aspects of traffic noise including the effect on the environment, sources and characteristics of noise and so on. Important points relevant to commercial vehicles are that turbocharged diesels are quieter than naturally aspirated types in most conditions, that bore size is more important than swept volume in determining the level of noise produced and that tyre and road • surface noise may become the principal noise sources if the engine level is reduced by 10 dB(A). And it is stated that a procedure to test stationary vehicles is being developed by the MoT for application at heavy goods vehicle testing stations. It is admitted that the measurement of individual vehicle noise at the roadside "is not easy".