Safety & Compliance · SOP

Hearing Conservation Audiometric Testing And Earplug Fitting

Standardized procedure for performing audiometric threshold testing and fitting hearing protection (earplugs) to prevent noise-induced hearing loss in industrial environments where noise levels exceed 85 dBA over an 8-hour time-weighted average.

Estimated Time

30 min

Difficulty

Intermediate

Regulation

CSA Z94.2 / WorkSafeBC

Version

1.0

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Purpose

This standard operating procedure establishes a consistent, auditable method for conducting audiometric threshold testing and fitting hearing protection (earplugs) to prevent noise-induced hearing loss among industrial workers. The procedure ensures compliance with provincial occupational health and safety regulations, including WorkSafeBC Part 7 and CSA Z94.2-14 guidelines. By standardizing the testing protocol, earplug selection, and fit-verification process, this SOP aims to reduce the incidence of Standard Threshold Shifts (STS) and maintain a hearing conservation program that meets or exceeds regulatory requirements.

Scope

This SOP applies to all personnel working in areas where noise levels exceed 85 dBA over an 8-hour time-weighted average (TWA), including production, maintenance, and warehouse operators. It covers baseline audiograms for new hires, annual audiometric surveillance, exit audiograms upon employment termination, and earplug fit-testing for all personnel using hearing protection. This procedure is also applicable to any worker who self-reports hearing difficulty or who has been identified through incident investigation as having potential noise overexposure. The procedure is not intended to replace diagnostic audiology evaluations conducted by licensed audiologists for pathological conditions.

Safety Precautions

LOTOLockout/Tagout: Ensure all machinery is locked out and tagged out before entering the testing area to prevent acoustic interference and electrical hazards from adjacent equipment.
PPEWear appropriate hearing protection (earplugs or earmuffs) during the entire procedure, including while assisting the employee and when outside the sound-attenuating booth.
BIOUse disposable hygiene covers on earphone cushions and probe tips for each worker. Replace covers between every test to prevent cross-contamination. Dispose of used covers in a lined waste receptacle.
CALVerify audiometer calibration daily using a biological check (the operator's own hearing thresholds) or an acoustic coupler. Reject testing if calibration drifts beyond ±5 dB at any test frequency.

Required Tools & Materials

Audiometer (diagnostic, Type 1 or Type 2 per ANSI S3.6–2018)
Sound-attenuating booth or enclosure (ambient noise levels below 40 dBA)
Otoscope with disposable specula
Disposable hygiene covers for earphone cushions and probe tips
Assorted earplug types: foam (e.g., 3M Classic, Howard Leight Max), premolded (e.g., E-A-R Ultrafit), and custom-molded options
Earplug fit-testing system with real-ear attenuation measurement (e.g., 3M E-A-Rfit Dual-Ear, Honeywell VeriPRO)
Training models and illustrated instruction cards for earplug insertion
Audiometric record forms (paper or electronic)

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Procedure: Step-by-Step

1 Pre-Test Preparation — Calibrate the audiometer daily using a biological check or acoustic coupler. Verify ambient noise levels inside the booth are below 40 dBA using a sound level meter. Obtain the employee's noise exposure history, including job tasks and years of exposure. Review the baseline audiogram if available. Confirm the employee has not been exposed to noise levels above 85 dBA for at least 14 hours prior to testing. Document the pre-test checklist on the audiometric record.

2 Otoscopic Inspection — Examine both ear canals with an otoscope. Check for cerumen impaction, infection, tympanic membrane perforation, discharge, or any abnormalities. Document all findings on the audiometric form. If significant cerumen blockage or active infection is present, refer the employee to a medical professional (audiologist or physician) before proceeding with testing. Do not test if the canal is occluded or if there is visible discharge.

3 Audiometric Threshold Testing — Seat the employee inside the sound-attenuating booth. Use the modified Hughson-Westlake ascending method to determine air conduction thresholds. Test frequencies in this order: 1000, 2000, 3000, 4000, 6000, 8000, and 500 Hz. Test the better ear (or the right ear if equal) first. Present a pulsed tone at 1000 Hz at 30 dB HL. If no response, increase in 10 dB steps until a response is obtained, then decrease in 5 dB steps until no response, then increase in 5 dB steps to confirm threshold. Record the lowest level at which a response occurs on at least two of three presentations. Repeat for each frequency.

4 Record Thresholds and Determine STS — Document the threshold for each frequency in each ear on the audiometric record. Compare results to the baseline audiogram using standard threshold shift criteria. A Standard Threshold Shift (STS) is defined as an average change of 10 dB or more at 2000, 3000, and 4000 Hz in either ear. If an STS is detected, flag the record for repeat testing within 30 days and notify the employer's health and safety representative. If no STS is detected, proceed to earplug fitting.

5 Earplug Selection and Fit-Testing — Select an appropriate earplug type based on the employee's noise exposure level (targeting an achieved PAR of at least 15 dB at 2000 Hz), job tasks, and individual ear anatomy. Using an objective fit-testing system (e.g., 3M E-A-Rfit Dual-Ear or Honeywell VeriPRO), measure the Personal Attenuation Rating (PAR) for each ear. The minimum acceptable PAR is 75% of the manufacturer's Noise Reduction Rating (NRR) for the specific earplug model tested. If the PAR is insufficient, select a different earplug model or size and repeat fit-testing until the minimum is achieved.

6 Training and Demonstration — Instruct the employee on proper earplug insertion using the hand-over-head reach method for foam plugs: roll the plug into a thin crease-free cylinder using clean fingers, reach over the head with the opposite hand to pull the pinna upward and outward, insert the plug deep into the ear canal, and hold it in place for 30–40 seconds until fully expanded. For premolded plugs, demonstrate the correct insertion and seating technique by pulling the pinna and twisting the plug into the canal until a seal is achieved. Verify the fit visually and using the fit-testing system. Provide the employee with the manufacturer's instruction card.

7 Documentation and Follow-Up — Record all results in the employee's audiometric record, including baseline, annual, and exit audiograms. Document the earplug model, size, and measured PAR for each ear. Issue the employee their assigned hearing protection and schedule the next annual audiometric test. Provide a copy of the audiogram to the employee and advise on hearing conservation practices, including proper insertion, maintenance, and replacement intervals for earplugs. File the complete record in the employer's health and safety system for a minimum of 10 years after employment termination.

Hearing Conservation Audiometric Testing And Earplug Fitting

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