Assessment of Noise Levels of Indian Tractors and its Effect on Hearing Capability of Operators

摘要

The Bruel and Kjaer impulse precision sound level meter number 2209 with one third octave band filter set was used to measure noise levels of Indian tractors in the field while operating farm machinery. The noise levels were measured by positioning the microphone close to the ears of the operators. Although the noise levels ranged from 89 to 93 db(A) for different operations like ploughing etc., but for operations normally carried out as usual practice it ranged from 92 to 93 db (A). Further 163 tractor operators belonging to villages near Ludhiana, who had no history of exposure to excessive noise except of farm machinery, were audio metrically examined using portable audiometer (Arphi Mark III) and mobile sound proof chamber, to determine the extent of damage caused by excessively high noise level of tractors. During the study it was revealed that contrary to previous assumptions the tractor operators operate the tractors much longer than 8 hours a day during sowing and harvesting seasons and some times even for more than 24 hours continuously in case emergencies arising out of vagaries of weather. Permanent threshold shift was observed in almost all the audiograms. All the audiograms are convex downward indicating more loss at higher frequencies. In general the deterioration in threshold of hearing increased with the increase in duration of noise exposure.