High-frequency hearing loss in male farmers of Missouri.

Farmers are exposed to noise that is potentially hazardous to hearing. We measured the hearing of 161 male farmers and 75 male nonfarmers at the 1979 Missouri Farmers Association Agri-Fair and compared it with the hearing of 129 office workers from central Missouri. Fixed-level screening tests were conducted in both ears at three stimulus frequencies: 1000 and 2000 hertz at 20 decibels hearing level and 4000 hertz at 25 decibels hearing level. Audiometers were calibrated in accordance with the ANSI-1969 standard. The results show that farmers are at risk for hearing loss at 2000 and 4000 hertz when compared with office workers. The prevalence of hearing loss was greater for farmers at both frequencies in every decade age group from 25 to 64 years. Using screening failure at 2000 and 4000 hertz in both ears as a criterion for a loss that would affect communication ability, we found that the failure rate was 16.8 percent for farmers and 6.2 percent for office workers. As other investigators have found, the prevalence of high-frequency hearing loss in male nonfarmers who associate with farmers was nearly as great as for farmers.