Achieving New Pass-By Noise Regulatory Norms R51.3 (Method B) - An Analysis of Acceleration and Noise Source Contribution

Worldwide automotive sector regulatory norms have changed and become more stringent and complex to control environmental noise and air pollution. To continue this trend, the Indian Ministry of Road Transport is going to impose new vehicle exterior pass-by noise regulatory norms R51.3 (Method B) in the upcoming year to control urban area noise pollution. This paper studies the synthesis of M1 category vehicle driving acceleration, dominant noise source, and frequency contribution in exterior PBN level. A vehicle acceleration analysis study was carried out to achieve an optimized PBN level based on the vehicle’s PMR ratio, reference, and measured test acceleration data. Based on the analysis, the test gear strategy and acceleration were changed to achieve a lower PBN level. Improved engine calibration resulted in a 20% increment of ith gear acceleration. This increased acceleration surpassed the upper limit of the reference acceleration range; hence, the vehicle was tested in a combination of both gear (ith and ith+1) conditions. With this study, a 1dBA noise improvement was achieved in overall PBN level. Furthermore, an exterior pass-by noise source contribution analysis was carried out for acceleration and constant speed test conditions. The engine was the first dominant noise source, and its mid-frequency noise had a higher contribution. With the help of acoustic encapsulation, a 1dBA noise improvement was achieved in overall PBN level. A source frequency analysis was then carried out for higher intake noise, and a low-frequency resonator was developed to reduce intake system noise, achieving a 1dBA noise improvement in overall PBN level. The output of this work was a reduction in the 3dBA pass-by noise level of the vehicle as well as significant improvement in in cab NVH performance. These potential solutions could be easily implemented on vehicles. With this approach, OEMs could achieve the new PBN regulatory norms for all existing and upcoming projects.