Roadside noise level and its association with traffic volume in Chattogram city, Bangladesh>

This study focuses on assessing noise pollution scenarios on major road corridors of Chattogram City, developing empirical noise models to predict the noise level from traffic flow, and identifying the traffic mode that affects the noise level the most. Noise measurements and traffic counts are carried out at 41 locations along four major road corridors of Chattogram City on three different sampling periods (weekday peak, weekday off-peak, and weekend). The quantitative noise assessment identifies that the equivalent noise level (L_eq) is above the recommended noise standard level set by Bangladesh Noise Pollution (Control) Rules in all surveyed locations, with the highest L_eq of 91.4 dBA and the lowest L_eq of 69.9 dBA. According to the noise related human health effect categorization, most of these surveyed locations are within moderate risk zone. The relationships between noise level descriptors (L_eq, L₁₀, L₉₀, NC, and TNI) and traffic volume are established using multiple linear regression, ridge regression, and mixed effects model. All noise level descriptors-related models are found statistically significant, indicating the possible association between noise level and traffic flow in the road corridors. A positive association between the equivalent noise level and the traffic flow indicates that increase in the traffic flow in Chattogram city deteriorates the sound pollution scenario. Interestingly, light vehicle volume has appeared to be the most influencing parameter to affect the noise level. The accuracy of the noise level parameter models is the best using the mixed effect approach. However, models with better goodness-of-fit are obtained when the rapid and short-duration instantaneous noise events are removed from the dataset.