Control of vehicle noise through legislation can play a significant role in reducing the negative impact of transport on the community. Presently the noise from all new road vehicles is currently controlled through the process of type-approval at the time of production. However, once a car or motorcycle is in-service there are very few accurate checks on the noise produced, and some vehicles are modified using after-market products.
The Department for Transport (DfT) currently receive a large number of complaints about the noise from individual vehicles, focussing on noise from exhaust systems.
DfT therefore commissioned TRL to review in-service noise measurement techniques in other countries and develop a simple noise measurement technique for use in the UK in order to assist roadside enforcement of Construction and Use Regulation 54.
The project was divided into two phases.
Phase 1 reviewed current literature in the subject area, performed an overall assessment of the problem, identified currently used and potentially usable in-service noise measurement techniques and assessed their suitability.
Phase 2 evaluated the recommended tests, including their relation to type-approval levels, and made further recommendations for an in-service test method that could be undertaken at roadside locations for enforcement purposes.

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