Tractor noise exposure levels were measured for bystanders as described by the Nebraska Tractor Test Laboratory and for bean-bar riders on ground surfaces of concrete, grass, and bean field. The influence of ground configurations, engine speeds, and gear selections on noise exposure levels were determined. The average sound level decreased as the ground cover changed from concrete to grass and then to bean field. An increase of 3 dBA was measured for engine speed changes from 1200 to 1500 rev/min and 1500 to 2000 rev/min. Gear selection was determined not to be significant for bystander exposures but bean-bar exposures increased as gear selection changed from first to fourth. Noise exposure levels experienced at the bean-bar position were, on average, 10 dBA higher than those measured at the bystander position. Results of the noise exposure measurements indicate that a hearing conservation program according to the Occupational Safety and Health Administration Compliance Manual (Petersen, 1979) should be established for bean-bar riders.
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