Study of vehicle noise for different operating conditions

The noise emission level from a vehicle is significantly influenced by different driving conditions and drivers’ behaviour. Almost all the in practice road traffic noise estimation models do not differentiate between different operating conditions. In this study, noise measurements are performed (on a small sample of one heavy and two light vehicles) to study the influence of different driving conditions on vehicle noise. Both pass-by and coast-by measurements are performed along with noise measurements for idle vehicles. Different operating conditions are considered so as to reproduce the vehicle noise in urban and freeway network. For pass-by measurements, the parameters measured are vehicle operating gear; harsh/smooth driving condition; speed profile of the vehicle motion and corresponding peak value of the noise level (at 7.5 meter from the test track and 1.2 meter above the ground). Each of these parameters are transformed and aligned for the data analysis. Pass-by measurements provide the information for total sound power level (PWL) of the vehicle, whereas coast-by and idle vehicle measurements provide the rolling sound power level (R-PWL). It is observed that the PWL difference between harsh and smooth acceleration is noticeable and it can be around 5 dB(A). Accelerating vehicle has more noise than cruising under the same speed and the difference between them can be around 10 to 15 dB (A) for smooth and harsh acceleration, respectively. R- PWL for heavy vehicle is more than that of light vehicle and the difference between them is of the order of 9 dB (A). Based on the measurements, further research direction is provided.