Headphones being properly placed as part of a hearing test.

Listen well to this cautionary tale about the surprising results from Bill’s annual hearing test.

Bill has worked at the Yourtown mine in various positions for 17 years. Because of his tasks, for the past 15 years, he has been enrolled in the mine’s hearing conservation program. He received his baseline audiometric testing upon enrollment in 2004. He’s had annual audiometric testing every year. A mobile test provider usually does his tests on site, and always at the beginning of the shift. Bill chooses his seat within the four-person test booth, places the headphones over his ears, and presses the response key to start the automated procedure. After the test, the mobile company provides training on noise avoidance and using hearing protection. The hearing conservation program administrator interprets the results, and that administrator changes several times during Bill’s tenure due to job turnover.

When the mobile provider is unavailable, Bill is sent to an off-site clinic. There, an audiologist places the headphones over Bill’s ears and completes the required test. An audiologist provides the hearing test through a standard protocol used for all patients at that particular clinic. Bill has used the off-site clinic five times over 15 years, but he hasn’t been there for four years. This year, in 2019, Bill’s annual test at the off-site clinic reveals a standard threshold shift in his left ear, showing he has substantial hearing loss compared to his baseline testing in 2005.

Bill is confused and angry — he dutifully had his hearing tested every year and he did everything the company required, but he still has substantial hearing loss. What happened?

Annual hearing tests are required under the Occupational, Safety and Health Administration (OSHA) and Mine Safety and Health Administration (MSHA) regulations as part of any hearing conservation program. Usually, these tests are provided, a comparison is made to the baseline test, then the records are marked as complete until the next year. However, as represented by Bill’s story, conducting the hearing tests without considering certain factors can lead to unexpected and distressing results. Avoiding four common pitfalls will help companies follow best practices for annual audiometry testing.

Have Hearing Tests Performed at Different Shift Times

To understand this concept of when hearing tests should be performed, a distinction must first be made between a temporary threshold shift and permanent threshold shift. A temporary threshold shift is a short-duration change in hearing after exposure to noise. The ear recovers to its previous condition after some period of time with little or no noise exposure. When a permanent threshold shift occurs, the ear does not recover.

To ensure accuracy and by OSHA and MSHA mandates, baseline tests are to be given when the worker has been noise-free — at the start of the shift before the worker is exposed to noise. When annual hearing tests are given after a baseline has been established, the National Institute for Occupational Safety and Health (NIOSH) recommends giving these annual tests mid-shift or end-of-shift. Mid-shift testing allows the tester to recognize any temporary changes or determine if hearing loss is from continued noise exposure or other factors.

If a threshold shift is found during an annual hearing test, the worker is referred for a retest. Importantly, this retest should occur when the worker has been noise-free (i.e., prior to any noise exposure that day) to confirm whether there is a threshold shift. If no threshold shift is found on the retest, then the annual audiogram identified a temporary threshold shift due to noise exposure during the shift. In this case, the worker can be retrained, fit-tested for hearing protection, and provided with a recommendation for noise remediation, with the goal of reducing the chance for a permanent hearing loss.

If the retest continues to show a threshold shift, this worker has likely suffered a permanent hearing loss, either from noise exposure at work or elsewhere. The same actions can be taken — retraining, fit testing and recommendations — with the goal being to preserve and protect their remaining hearing.

Without a mid-shift or end-of-shift hearing test, any temporary changes in hearing due to occupational noise exposure will not be identified. Performing the annual hearing test mid-shift or at the end of the shift, with a subsequent non-noise exposed test at a later date should it be needed, will allow for easier identification of temporary changes in hearing.

Consistently Use the Same Test Provider Year-to-year

Several options exist for hearing conservation program audiometric testing. In-house testing, done by someone employed by the mining company, can lend consistency. However, that individual may not always have the skills necessary to provide and interpret the audiogram, or that individual may change over time.

A mobile company will conduct audiograms inside a specially outfitted vehicle or with other mobile equipment. They may also have a more knowledgeable test giver. However, because of the volume of testing done by mobile companies, the equipment could suffer from wear and tear and follow-up scheduling may be difficult.

A standalone clinic that performs audiometric testing will likely have the most knowledgeable test giver. However, traveling to a clinic may be difficult for workers and makes a mid-shift hearing test difficult. Plus, even a standalone clinic may be unfamiliar with hearing conservation audiometry needs tailored to miners. Also, if a clinic is a for-profit hearing aid dispenser, the recommendations may be influenced by that interest.

Given the above issues, considering the option that provides the most consistency for the mine and the workers is the best approach. This allows for a better exchange of information and possibly more trustworthy results.

Make Comparisons Beyond the Baseline

MSHA and OSHA requirements for audiometric monitoring are to compare annual tests to the baseline to determine a threshold shift. While this comparison provides information on the presence of a threshold shift, other factors that affect the reliability of the audiometry can be missed. ANSI Technical Report S12.13 suggests several other comparisons to ensure a reliable audiometry, as described below.

While the average hearing conservation program administrator might not use the ANSI Technical Report, it details several approaches that can be easily implemented into an existing program and do not require audiometric expertise. For example, checking results from the previous year — not just against the baseline — can identify unusual results such as an accidental reversal of readings for the left and right ears or an improvement in hearing. Also, useful trends across test takers and equipment can be identified. For example, if all workers show decreased performance in the left ear, even if not to the degree of a standard threshold shift, an equipment problem is likely.

Ask Providers About Their

Testing Procedures

Certain errors can be avoided by asking about the provider’s standard operating procedure. If providers double-check equipment and headphone placement, this helps prevent a source of errors that can easily be identified. This may seem like the most obvious source of error, but it is often ignored — especially if multiple workers are tested simultaneously or if the test giver does not perform the headphone placement.

In particular for automated tests, where multiple testing stations may be used, a test taker might choose the wrong response button synced to a different testing station, thereby producing inaccurate results. Also, if the test taker places the headphones incorrectly over his or her ears — headphones are typically color-coded with red for the right ear and blue for the left — then pressing the response button to indicate that an auditory stimulus was heard in the right ear will actually indicate that it was heard in the left ear, and vice versa.

Best Practices Equal Best Results

Ensuring that audiometry is reliable and valid helps gauge the success of the hearing conservation program as a whole. If testers are confident that their audiometric testing results are valid and that standard threshold shifts have occurred, they can then feel confident in their decision to investigate other aspects of the hearing conservation program. However, with incorrect audiometric data and inconsistent practices, testers can’t know if changes in hearing are real or due to testing factors. By ensuring audiometric accuracy, a company’s hearing conservation program can avoid becoming a hearing loss documentation program.

Disclaimer

The findings and conclusions in this paper are those of the authors and do not necessarily represent the official position of the NIOSH, Centers for Disease Control and Prevention.

Amanda Azman is a research audiologist with NIOSH. Joseph Schall is a health communications specialist with NIOSH. For more information, contact mining@cdc.gov.