Species-Related Difference to Noise Reduction Between Trees in Urban Forest: The Abidar Forest Park (Case Study)

Sound pollution is one of the most important urban problems which endangers mental and physical health of the residents. This study was aimed to assess the influence of different tree species, including Fraxinus rotundifolia, Robinia pseudoacacia, Platanus orientalis, Platycladus orientalis, and Pinus eldarica, in reducing noise pollution in the Abidar Forest Park. A further objective was to identify the contaminated areas of Sanandaj city and to propose suitable noise absorbent tree species in consistent conditions. For each tree stands the noise measurements were performed during intervals at frequencies of 250, 500 and 1000 Hz, besides an open area with the same topography. With regards to the second purpose, a total of 50 stations with residential, commercial, residentialcommercial, and green space applications were selected across the city. Equivalent Continuous Sound Pressure Level (Leq) was determined in five replicates for 30 min. The measurements were performed under stable weather conditions and low wind velocity at 17:00 (traffic peak) in summer and fall. All of the Leq values were above the threshold noise level. The highest noise reduction was recorded in summer (i.e., green season); Platanus and Platycladus species demonstrated the highest and lowest noise absorption (31.43 dB and 22.28 dB, respectively). Furthermore, a meaningful difference was observed between Leq values of commercial, residential, commercial-residential, and green space urban applications, and the central parts of the city showed noticeable noise pollution. Taken together, due to being exposed to higher than the acceptable threshold noise level, the residents of Sanandaj will be endangered to health problems in the near future; thus consideration should be given to the noise pollution sources.