Effects of audiometric threshold step size on proposed ANSI S12.13 outcomes for characterizing hearing conservation program effectiveness.

Audiometric records of 213 employees with low noise exposure were selected from the public domain data base underpinning Draft American National Standards Institute (ANSI) S12.13-1991 Standard Evaluating the Effectiveness of Hearing Conservation Programs. Records were selected from an ANSI S12.13 "control" group demonstrating raw audiometric thresholds in 1-dB steps, presumably resulting from self-recording audiometry. Raw audiometric data were rounded to the nearest 5-dB step, and ANSI S12.13 analysis protocols were applied to both raw and rounded data sets. The magnitude of all proposed ANSI test statistics increased with audiometric step size. Percent worse sequential and percent better or worse sequential protocols were markedly more sensitive to threshold step size than standard deviation of difference thresholds. The direction and magnitude of change in these outcomes supports the assumption that criterion ranges in the draft standard hold artifactual bias against hearing conservation programs (HCPs) collecting audiometric data in 5-dB steps.