Observation and Prediction of Noise Levels in Residential Areas Surrounding Power Generators in Najaf, Iraq

ABSTRACT: The key objective of this work is to investigate the impact of noise from generators on a residential area in Najaf, Iraq and to determine the optimal distance between the generator and the residential area. To achieve this objective, predictions were conducted and observations were collected at 3 downwind distances (7 m, 20 m, and 50 m) from the generator on selected dates of winter and summer (Jan 25-28 and Feb 1 and 10 and June 13-14, 2025). The observations showed that when the generators were in operation, noise levels exceeded the Iraqi standard and WHO guidelines. However, when the generators were not in use but the national grid was in operation, noise levels were below the Iraqi standards, except for maximum levels. In the absence of noise from the generators and national grids, the noise levels were below the standards. The noise generally decreased by 8 dBA when moving from 7m to 20m from the generator, and by 3 dBA when moving from 20 to 50 m. There was a negative relationship between wind speed and temperature on one hand, and noise level on the other hand, with a correlation coefficient of 0.45 to 0.65 with wind speed and 0.65 to 0.7 with air temperature. In contrast, the correlation with the relative humidity was positive (0.68). Also, a simple model was applied to analyze noise dispersion over a domain of 400m. The optimal distance estimated by both modeling and linear regression to meet the Iraq daytime standard of 60 dBA is 75 m and to meet the Iraqi nighttime standard of 50dBA is 120m. The results showed the predicted LAeq were overpredicted by 2% at 7m but underpredicted by 3% and 5% at 20m and 50m, respectively.