Traffic Noise Modelling Considering Traffic Compositions at Roundabouts

As the traffic volume is increasing in urban areas, their major effect can be seen in terms of noise near roundabouts. An effort has been made in this work to evaluate the noise level near a roundabout in terms of certain noise-level descriptors such as Leq, L10, L50 and L90 to estimate the maximum and pervasive noise climate existing at the roundabouts. Multiple regression analysis technique is used to form a model for each of the sound-level descriptors for a roundabout and factors are found that are significant for a particular sound descriptor. Three roundabouts are considered for analysis of varying traffic volume and geometry of roundabout; these were Y.P.S. Roundabout, Thikkari Roundabout, and Fountain Chowk Roundabout, Patiala. The R2 values were found to be 0.70 for Leq, 0.79 for L10, 0.78 for L50, 0.84 for L90 indicating a good correlation. The percentage error was found to be varying between ±3% for all the sound descriptors. “2t-test” was carried out for 25 samples and no significant difference between predicted and measured sound levels was found. A 1/1 octave analysis was done to determine the frequencies that were dominating. Peak noise level at roundabouts was obtained to be at 500 Hz., 1 kHz., 2 kHz., and 4 kHz. These correspond to maximum annoyance range and therefore there is a need for mitigation measures.