Julia D. Royster
Environmental Noise Consultants, Inc., P.O. Box 30698, Raleigh, NC 27622-0698
Larry H. Royster
NC State Univ., Raleigh, NC 27695
Percentile distributions of hearing levels by age have been developed for male and female subjects in the black and white NINEPs which were originally published as mean data [L. H. Royster and W. G. Thomas, Am. Ind. Hyg. Assoc. J. 40, 504--511 (1979); L. H. Royster et al., Am. Ind. Hyg. Assoc. J. 41, 113--119 (1980)]. These reference populations were screened to exclude persons with more than 2 weeks of occupational noise exposure, but they include all other age-effect influences: Nonoccupational noise exposure, pathology, and presbycusis. The results for white subjects are similar to the U.S. Public Health Service data in Annex B of international standard ISO 1999:1990 (E). However, black subjects exhibit much better hearing, similar to the screened presbycusis data in Annex A of ISO 1999:1990 (E). The difference in threshold distributions will be explored for the better ear versus the binaural average, and for subgroups with different characteristics.