Investigating of environmental traffic noise modelling by using FHWA TNM in Tehran township

There are several noise modeling software packages in order to predict noise level, each of them has different accuracy in different country. The present study was undertaken to analyze Traffic Noise Model software package (TNM) for two large highway in Tehran township. Firstly, field measurement for equivalent noise level (Leq) was carried out by sound level meter(SLM), then Leq prediction by the software was done. Finally, the results of the two previous steps were compared. the mean deviation of the results for sound levels below 80 dB was 0.33 dB, but for values further than 80 dB, the deviation was high. due to the obsolescence of a large number of the trucks inside Iran, new trucks instead of using software-defined trucks, were defined. With this change, the modeling and measurement results were more coordinated. The coefficient of determination (R2) increased from 0.4915 to 0.7312