- ISHN GLOBAL
- EHS RESEARCH
We may, however, be turning a corner. New methods and technologies have the potential to actually eradicate noise-induced hearing loss through a more personalized and more measured approach to hearing conservation.
A new way forward
The first sign that a new approach was needed was the recognition that hearing protectors â€” specifically earplugs â€” weren’t providing the protection they claimed. It wasn’t anything wrong with the products.
Tested in the lab under “ideal conditions,” they blocked, or attenuated, just as much sound as their noise reduction ratings (NRR) said they would. But in the field, when real workers wore them, they blocked much less noise â€” and sometimes none at all.
A number of schemes were proposed to “derate” hearing protectors â€” sometimes by 50 percent or more. Critics warned, however, that de-rating risked overprotection. Overprotected workers might miss important warning sounds or be unable to communicate effectively with supervisors or fellow workers, and as a result, would actually wear their hearing protectors less often. Or, in some scenarios, workers would be required to wear dual protection â€” an added expense to the safety budget â€” when single protection should be adequate.
In response, the EPA is expected to announce new labeling requirements for hearing protectors. There will still be an “NRR,” but it will now be a two-number range instead of a fixed, singlenumbered rating. And while it will still be based on laboratory testing, test subjects will be trained by the experimenter on the earplugs’ or earmuff’s use, and then fit themselves with the HPD.
Personalize the experience
While many workers do not achieve the published attenuation from their hearing protectors, this is by no means universally true. One study, conducted on over 100 employees at eight different facilities, showed a direct correlation between earplug fit and effective attenuation.
Workers were tested using their own unmodified earplugs and with no additional training or coaching. Fully one-third achieved attenuation higher than the published NRRs for their earplugs, another third achieved attenuation within 5 dB of those ratings, and only the bottom third had attenuation that was more than 5 dB below published NRRs
This raised the question: “If good fit results in good attenuation, what factors contribute to good fit?” In analyzing the interview data, only one factor had a strong correlation: one-onone training. The more often an employee had received individual training in the proper use of hearing protectors, the higher the probability that he would achieve a good fit, and hence, good attenuation.
Also noted anecdotally was that the louder the noise hazard a worker was exposed to, the more attentive they were to wearing their hearing protectors and fitting them properly.
Thus, regardless of how hearing protectors are rated, one principle of the new personalized approach to hearing conservation is to incorporate individual fit-training sessions into the training program.
This does not eliminate the need for group training. In fact, group training can reinforce the one-on-one sessions by ensuring that all workers buy into the company’s program and practices.
Fit testing made easy
Until recently, it was difficult to determine how much attenuation a hearing protector was actually delivering. Fit testing was relegated to laboratory settings, a fact that precluded its use as part of a normal hearing conservation program. Recently, however, several new fit testing systems have been introduced that make it easy to get a real-world, personalized picture of an employee’s ability to use his or her earplugs.
Some sophisticated systems use “loudness-balance” technology that works with unmodified earplugs of any type. This can help determine whether an employee receives optimal protection for his noise environment, requires additional training, or needs to try a different model. Using simple tests, these systems can quickly determine an employee’s personal attenuation rating (PAR) of how much attenuation they receive from their earplugs.
This approach allows personalized fit testing to be readily incorporated into the training regimen of a hearing conservation program. The National Hearing Conservation Association (NHCA) and OSHA have even endorsed fit testing as a recommended tactic in reducing occupational hearing loss and as a metric to assess an HCP’s overall effectiveness.
New technologies measure noise exposure
New innovations are taking the concept of optimizing attenuation a step further by providing workers with real-time control over their noise exposure right in the workplace. Sound level meters have long been used, along with personal dosimeters, to measure noise levels. Sound level meters indicate ambient noise, while personal dosimeters, with microphones mounted close to the worker’s ear, measure individual ambient exposure for that worker as he goes about his daily tasks.
Personal dosimetry does not provide any information on individual noise dose or the exposure over time while wearing hearing protection. However, recent advances in in-ear dosimetry now make it feasible to measure the protected noise dose of workers who wear hearing protection. These technologies record daily noise exposure levels for workers under their hearing protectors to provide an accurate and complete measurement of personal noise dose. Unlike personal dosimeters that require decision-making based on estimates, in-ear dosimetry provides precise real-time data for each worker.
Integrated into earplugs or earmuffs, in-ear dosimetry measures and records the worker’s actual noise dose â€” both while they are wearing protection and while they are notâ€”over their entire work shift. This real-time monitoring alerts workers when their noise dose approaches or exceeds safe limits. It lets them know how well their hearing protectors are performing and when they need to wear them. Thus, workers have real control over their hearing protection, in real time.
In-ear dosimetry has been proven highly successful, both in terms of reducing the progression of occupational hearing loss and increasing the overall efficiency of a hearing conservation program. Thus far, in-ear dosimetry has proven to be the only metric with a direct potential to measure and prevent further noiseinduced hearing loss from on-the-job exposures.
Numerous other studies have shown the importance of providing HPDs that are comfortable during long work shifts and that are appropriately matched to noise levels so employees can communicate effectively. It is also important to offer a comprehensive variety of HPDs from which employees can choose. These and other elements are all valuable components of an OSHA-approved hearing conservation program.
But without convincing workers of the need for hearing protection and then providing them with the means to assure optimal attenuation from their HPDs, even the best program is doomed to failure. By showing workers the need and giving them the tools to affect their own protection, a measured, personalized approach to hearing conservation can finally help us turn the corner on occupational noiseinduced hearing loss.