ANALYSIS AND MODELILNG OF ROAD TRAFFIC NOISE IN ONITSHA METROPOLIS, NIGERIA

Abstract

Despite the enactment of legislations and efforts by the government to stem vehicular noise, the predominant source of noise pollution in urban areas, the noise exposure of people of Onitsha Metropolis, has hardly changed; rather it appears to increase by the day due to the growth of vehicular population. This study selected 12 areas for investigation; these are: 2 commercial centers, 3 road junctions/busy roads, 3 passenger loading parks and 2 high-density and 2 low density residential areas with noise measurements being done in the morning (8.am 9.00am), at noon (11.00 12.00pm), during afternoon (2.00pm 3.00pm) and in the evening (5.00pm 6.00pm) to determine noise pollution all over the metropolis. Noise descriptors such as L₁₀, L₉₀, L_Aeq, TNI, NPL (LNP) and NC were assessed to reveal the extent of noise pollution due to heavy traffic and failures of some mechanical systems in the metropolis. The road junctions had the highest noise pollution levels, followed by commercial centres, passenger loading parks, high density residential area and finally low density residential area which were found to be much beyond the permissible limit (70dB during the day time).Chi-square (X²) test was also computed for investigated locations at different times to infer the level of significance. The tests depicts that the noise levels of different locations do not differ significantly at the peak hour. Again, prediction model was used to predict equivalent noise level. Comparison of predicted equivalent noise level with that of the actual measured data demonstrated that the model used for the prediction has the ability to calibrate the multi-component traffic noise and yield reliable result close to that by direct measurement. Many solutions proposed for noise control in the city are enumerated as a map of noise pollution was developed for Onitsha from the measured noise values.