noise pollution and traffic noise index on mashhad main streets during the busiest hours of summer

introduction: among the environmental pollutions, noise is very important for its physiological  and psychological effects on human. traffic noise is one of the most important pollutants and the  hospitals  are  one  of  the  critical  places  regarding  this  type  of  noise.  for  these  reasons,  in  the  summer  of  1382,  the  traffic  noise  of  mashhad  main  streets  around  the  hospitals  was  assessed  during the busiest hours.  materials and methods: the noise indexes such as l aeq , l afmax , l 10 , l 50  and l 90  were measured  by a sound-level-meter, model investigator 2260. the traffic load was also determined. on the  basis  of  these  results,  noise  pollution  level  (npl)  and  traffic  noise  index  (tni)  were  calculated. the assessment was done during three different periods of the days in twelve stations.   results: based on the obtained results, the maximum l aeq  was recorded on bahar street during  the morning hours and on koohsangi street during the noon and night periods. throughout the  three  periods  the  maximum  npl  and  tni  were  estimated  on  bahar  and  nakhrisi  streets,  respectively.  the  correlation  between  all  of  the  indexes  was  analyzed  and  a  logarithmic  correlation was observed between l aeq  and the traffic load.   discussion  and  conclusion:  on  the  basis  of  the  noise  standard  in  free  field  in  iran,  noise  pollution is a serious problem in mashhad.