The 85 and the 90
Under OSHA 1910.95, exposure at 85 decibels as an 8-hour time-weighted average triggers the hearing conservation program, and exposure at 90 decibels, the permissible exposure limit, requires engineering or administrative controls on top of it. Exposures are computed without credit for hearing protection, so the measurement is of the noise itself, not the earmuff. The OSHA oil and gas eTool and industry guides put compressors, mud pumps, generators, and drilling equipment well past the action level on a normal shift.
The five elements
The program has five parts: noise monitoring to identify who is over 85, audiometric testing with a baseline and annual tests, hearing protection that is provided and worn, training and education, and recordkeeping. A standard threshold shift on an annual audiogram triggers follow-up, and the employer must act on it. In the field, the failure point is usually the same: earmuffs come off in the heat, and nobody fits, checks, or enforces wear.
The audiogram is the evidence
Without a baseline test within six months and annual tests after that, the program cannot be proven and the shift in a worker's hearing cannot be documented. NIOSH describes noise-induced hearing loss as permanent and entirely preventable. The audiogram file, the training log, and the hearing protection issuance record are the three documents an inspector asks for, and they are the same three that tell a company whether the program is real.
Hearing conservation belongs with the other routine protections on a lease: job safety analysis, H2S monitoring, and incident investigation. All of them depend on dated records that survive an audit. If training dates and audiograms are scattered across filing cabinets, an operations audit will show which programs are documented and which are assumed.