Since the early 1970s new motor vehicles have been subject to type approval test procedures that limit noise emission. The lack of a closer correlation between type approval noise limits and traffic noise emission levels has been attributed, in part, to the test procedure that is used for type approval. Recently work has been carried out to develop the vehicle noise test procedure. For example, ISO Working Group TC 43/SC1/WG42 is revising the basic test method described in the original ISO standard (ISO 362). Concurrently, the UN-ECE Working Group WP29/GRB is updating its method of testing road vehicles (Regulation 51). It is clear that future vehicle noise test procedures will need to ensure a greater degree of correspondence between test results and noise generation in practice. In other words, test procedures will need to offer a better degree of discrimination between noisy and relatively quiet vehicles for conditions representative of noise intrusion in residential areas. Future testing will also need to ensure that appropriate examination of both propulsion and rolling noise components are considered. In addition any future test procedure should be appropriate for new and emerging technologies such as alternative fuelled and hybrid powered vehicles. The Department for Transport commissioned TRL to examine the technical issues associated with the range of test procedures that could be considered for current and future vehicle noise testing. This report describes the comprehensive test programme that was undertaken and the results obtained. Test were conducted under pass-by and stationary conditions on 26 vehicles including 5 HGVs, 4 buses, 5 minibuses, 4 vans and 8 cars, including 2 high performance sports cars. It also provides guidance on the most appropriate test procedures to use for vehicle type approval testing and indicates the noise level limits that should be achievable for different vehicle types.

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