MRO Magazine

Training key to hearing protector effectiveness, study shows (November 01, 2008)

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Smithfield, RI -- A recent field attenuation study conducted by the Howard Leight Acoustical Laboratory on the performance of hearing protection devices showed that individual, one-on-one training was...

Smithfield, RI — A recent field attenuation study conducted by the Howard Leight Acoustical Laboratory on the performance of hearing protection devices showed that individual, one-on-one training was the most significant factor in predicting good earplug performance.

The study, which was conducted on over 100 workers at eight different facilities, showed that fully one third of workers achieve attenuation higher than published Noise Reduction Ratings (NRR) for their earplugs, and that another third achieve attenuation within 5 dB of those ratings. Only the remaining third had attenuation that was more than 5 dB below published NRRs.

“This reinforces the need for individual fit testing of earplugs, especially in light of the Environmental Protection Agency’s proposed labelling changes,” said Brad Witt, MA, CCC-A, director of hearing conservation for Sperian Hearing Protection, LLC, and a principal author of the study.

“No generalized rating scheme for hearing protectors can be effective without knowing how much attenuation individual workers actually attain. If a safety manager were to supply earplugs based on the assumption that all earplugs only achieve half of their publishe NRR in the field, then clearly two-thirds of the workers in this study would be seriously overprotected, since they are achieving much higher protectio than 50%.”


In this study, workers were tested during their standard work shifts. They were not pre-screened, and were tested with their own earplugs that they routinel wear on the job, with no modifications The tested earplugs were from four different hearing protection device manufacturers, and workers received no training or coaching as part of the test. The workers were simply asked to insert the earplugs as they normally did on the job. No feedback or correctio was offered if they fit the earplug incorrectly.

According to Witt, the purpose of the study was to identify factors that contributed to good earplug fit, and hence, good attenuation in use. “A variety of personal as well as program factors were evaluated to determine which factors would correlate the best to A good earplug fit among these 100 workers,” he said. Factors evaluated included: gender; age; years working in A hazardous noise environment; ear canal size; familiarity with hearin protection devices; model of produc used; amount of group training received; amount of individual training received; and enforcement.

Of all these factors, said Witt, “only one stood out as having A strong correlation one-on-one training. That is, the more often A worker had received individual training in the proper use of hearing protectors, the higher the probability of A good fit.” The same could not be said for group training according to Witt. “It appeared to make no difference at all whether A worker had attended zero, five or 10 group training sessions in hearin protection, when measuring good attenuation in the field.”

Enforcement, he added, was also A good predictor of good earplug performance but only when it was coupled with one-on-one training.

Another question posed by the study was whether workers who achieved low attenuatio with one type of earplug would also attain low attenuation with all types of earplugs “We tested this by inviting some worker to try A second pair of earplugs — differen earplugs, perhaps A model they had never tried before,” said Witt. of a good fit Workers who tried A second pair of earplugs often had major leaps in attenuation, bringing them closer to the published NRR.

“Field testing of hearing protectors bridges the gap between the laborator estimates of attenuation and the real-world attenuation achieved by workers as they normally wear the protectors,” Witt concluded. “This test confirmed the value of individual, one-on- one training, and the wisdom of offering workers A variety of suitable hearing protectors.”

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