The baseline audiogram is the first and referenced audiogram against which future audiograms are compared. Employers must provide baseline audiograms within 6 months of an employee’s first exposure at or above an 8-hour TWA of 85 dB. An exception is allowed when the employer uses a mobile test van for audiograms. In these instances, baseline audiograms must be completed within 1 year after an employee’s first exposure to workplace noise at or above a TWA of 85 dB. Employees, however, are required to wear hearing protectors whenever they are exposed to noise levels above a TWA of 85 dB for any period exceeding 6 months after their first exposure until the baseline audiogram is conducted.
Baseline audiograms taken before the hearing conservation program took effect in 1983 are acceptable if the professional supervisor determines that the audiogram is valid. Employees should not be exposed to workplace noise for 14 hours before the baseline test or wear hearing protectors during this time period.