Development of a road shoulder's equivalent sound source traffic noise prediction model

The accuracy of traffic noise prediction models (TNMs) is impaired by affecting factors and system errors. In addition, the traditional traffic noise source cannot be tested as the sound source is generated in the centreline of the road. To address these limitations, a TNM based on the equivalent sound source at the road shoulder was developed. First, the equivalent traffic flow based on the acoustic-equivalent conversion coefficient was calculated and the traffic noise source intensity model was deduced. The shoulder's sound pressure level (SPL) data were then used to formulate a single-vehicle equivalent SPL model and correct the traffic noise source intensity model. The propagation model was fitted according to the attenuation law that traffic noise strength attenuates gradually from the shoulder to the road outside and fluctuates periodically. The results of a case study showed that the absolute percentage error of the proposed model's prediction was 2·3% compared with the measured value, which was better than the performance of the current model suggested in the Chinese specification. The proposed prediction model provides a friendly and less time-consuming approach for city planners and traffic engineers to conduct freeway traffic noise prediction and assessment.