Road traffic noise in downtown area of Tehran
Noise pollution is by now worldwide recognized as a major problem for the quality of life in urban areas. Vehicular traffic is the most important source of the environmental noise pollution in these areas (Zennin et at., 2001; Suksaard et at., 1999; Arana and Garcia. 1 998. The increasing in the population and in the number of circulating vehicles has led to an increase in the noise pollution but the noise pollution has been considered less than other contaminants in the environment. The need for studies regarding the urban noise pollution and its consequences on the environment has motivated various researches on the problem in several countries (Zeid et at., 2000; Zheng, 1996; Zannin et at., 2003). Many researchers have reported the noise level of the downtown areas of Tehran from 72 to 78 dBA( Nassiri and Pouransari, 1995). Urban traffic noise is one of the most pervasive types of noise pollution and generally considered more intrusive than other types of noise such as industrial noise, airport noise and community noise (Kryter, 1982; Zannin et at., 2003).