NHCA Professional Guide for Audiometric Baseline Revision

In a hearing conservation program (HCP), each employee’s baseline audiogram gives the reference hearing thresholds for that individual. The results of later monitoring audiograms are compared to the baseline to detect significant changes in hearing thresholds. When significant shifts for the worse are identified, follow-up actions are taken to improve employee protection from noise. As specified in the Hearing Conservation Amendment (CFR 1910.95) promulgated by the Occupational Safety and Health Administration (OSHA), the baseline may be revised by the reviewing audiologist or physician either for significant improvement in measured thresholds or for persistent standard threshold shift (STS). Because the baseline audiogram is so important for detecting hearing change and reacting to prevent additional change, NHCA assigned a special committee to develop guidelines for revising audiometric baselines. The 16-member committee conducted research and evaluated various strategies over several years. The guidelines given here, which were approved by the board of NHCA in March 1996, represent the consensus of the committee. Following these guidelines will provide consistency across professional reviewers and audiometric testing service providers, thereby increasing the degree of protection for noiseexposed workers. Note: although the guidelines require persistence of hearing changes before the baseline is revised, protective follow-up actions for the employee are needed as soon as significant changes for the worse are first shown.