Study shows individual training is the key to hearing protector effectiveness

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 in the US, showed that a third of workers achieved attenuation higher than published sound level conversion ratings (SLC80) for their earplugs and that another third achieved attenuation within 5 dB of those ratings. Only the remaining third had attenuation that was more than 5 dB below published SLC80s.

“This reinforces the need for individual fit testing of earplugs,” said Brad Witt, Director of Hearing Conservation for Sperian Hearing Protection and principal author of the study. “No generalised rating scheme for hearing protectors can be effective without knowing how much attenuation individual workers actually attain. If a safety manager was to supply earplugs based on the assumption that all earplugs only achieve half of their published attenuation in the field, then clearly two-thirds of the workers in this study would be seriously overprotected, since they are achieving much higher protection 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 routinely 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 correction was offered if they fitted the earplug incorrectly.

According to Witt, the purpose of the study was to identify factors which 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.”

Factors evaluated included gender, age, years working in a hazardous noise environment, ear canal size, familiarity with hearing protection devices, model of product 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. It appeared to make no difference at all whether a worker had attended none, five or 10 group training sessions in hearing protection when measuring good attenuation in the field.

“Field testing of hearing protectors bridges the gap between the laboratory estimates of attenuation and the real-world attenuation achieved by workers as they normally wear their protectors,” said Ben Elsey, Hearing Conservation Specialist for Sperian Protection Australia. “This test confirmed the value of individual, one-on-one training and the importance of new technologies like VeriPRO, recently developed by Howard Leight in conjunction with the House Ear Institute to measure real-world attenuation of unmodified earplugs and used as a means to improve individual employee training and enhance the overall effectiveness of hearing-conservation programs.

“It’s important to make an accurate, real-world assessment of employees’ earplug fit, which helps to providing individual training and is essential to achieving adequate attenuation.”