comparison of noise exposure levels on chainsawers in motor-manual tree felling (case study: hyrcanian forest)

chainsaw is an important machine for tree felling limbing and bucking in hyrcanian forest and the major problems related to using forest machines was sound intensity. the aim of this study was to measure the sound level in occupational exposure of workers, determine the exposure time of workers and comparison of the variables among the workers. this study was carried out in namkhaneh district in kheyrud forest. in this study, sound intensity chainsaw was measured every 10 seconds in under cut stage and every 15 seconds in back cut stage. results show that the workers were faced with the sounds upper the 85 db and time duration of exposure with noise of chain saw in tree felling was upper than the allowable limitation and standard. comparison of two worker, considering working time duration and the corresponding sound level, with allowable values of time duration and sound level, shown between under cut and back cut stages time durations are significant difference, such that generally in hornbeam (carpinus betulus) trees, in under cut stage inexperienced worker in %71 and experienced worker in %32 of working time duration and in back cut stage, experienced worker %10 and inexperienced worker in %54 of working time duration are faced with the sound level and time duration upper the allowable limitation, which these differences are corresponded to the working method and the worker experience.