(a) If an employee's hearing test (audiogram) reveals that the employee has experienced a work related standard threshold shift (STS), as defined in the instructions, and the employee's total hearing level is 25 decibels (dB) or more above the audiometric zero (averaged at 2000, 3000, and 4000 Hz) in the same ear(s) as the STS, the employer must record the case on the SH 900 log.