NIOSH HPD Well-Fit™: The Future is Fit-Testing

Categories: Agriculture, forestry, and fishing, Construction, Hearing loss, Manufacturing, Mining, Oil and gas, Personal protective equipment

May 31st, 2013 6:50 am ET - Captain William J. Murphy, Ph.D.; Dr. Mark R. Stephenson, Ph.D.; Captain David C. Byrne, M.S. CCC-A; Christa L. Themann, M.S. CCC-A

Photo courtesy of the U.S. Army Aeromedical Research Laboratory

Today is Save Your Hearing Day. For workers and others who are exposed to dangerously loud noises which cannot be reduced or eliminated, hearing protection devices (HPDs) are absolutely necessary to save their hearing. But if HPDs are not properly selected or correctly worn, the devices may not block out enough noise and the wearer may still risk a loss of hearing. How can a person tell if their HPDs are fit correctly? A new development from NIOSH – HPD Well-Fit^TM – can quickly and inexpensively test the performance of hearing protection. This fit testing technology is a huge advancement in efforts to save workers’ hearing.
HPD fit-testing is not a new concept, and several fit-testing systems have been developed over the past decade. However, until now, limitations of fit-testing technology have made it impractical to implement on-the-job.   Commercially-available systems require expensive specialized equipment and can take as long as 30 minutes to complete a test. For many employers, these barriers prohibit widespread implementation of fit-testing at their jobsite. Furthermore, some systems can only test certain HPDs or require specially-modified hearing protectors. NIOSH developed the HPD Well-Fit™ fit-testing system specifically to address these technical limitations and provide a feasible method to obtain measures of earplug performance in the workplace. HPD Well-Fit^TM utilizes technology that is built into just about every computer sold today, requires only 4-7 minutes to measure HPD performance, and can be used with any earplug.
Using the computer’s mouse as the input device and a high-definition audio output board, HPD Well-Fit^TM generates the sounds required to fit-test a worker’s hearing protector with the addition of sound-isolating headphones. The speed of the test makes it feasible to re-train and re-test the worker until mastery in fitting the protector has been achieved. HPD Well-Fit^TM incorporates PC-based video training especially developed by NIOSH for this purpose. This training has been proven to be both very quick and effective.   The Personal Attenuation Rating (PAR), a measurement of a hearing protector’s ability to reduce noise for an individual, is calculated using a unique algorithm developed by NIOSH scientists. As a result, HPD Well-Fit^TM makes it possible to quantify an individual’s noise exposure and ensure that it is safe, rather than relying on best guesses based on noise measurements and a general estimate of earplug attenuation. The impact of this capability on worker hearing health cannot be overstated, and recently won HPD Well-Fit^TM the NIOSH Bullard-Sherwood Award for Research to Practice.

HPD Well-Fit^TM has been tested in several field and laboratory studies. In February 2012, HPD Well-Fit^TM was used to assess the protection of inspectors and engineers responsible for off-shore oil drilling rigs in the Gulf of Mexico. These workers were exposed to noise levels of 110 dB(A) on a regular basis as they flew to and from the off-shore platforms in helicopters. Fit-testing was completed for 74 workers at four regional offices in the course of two days. Workers who did not achieve a PAR of at least 25 dB (sufficient to reduce their exposure to the NIOSH recommended exposure limit of 85 dB[A]) were reinstructed or refit with a different hearing protector to help them achieve an appropriate protection level . As Figure 1 shows, 92% of the workers were able to achieve the 25-dB PAR. Due to time constraints, it was not always feasible to hold the workers after their assigned shifts and some that were close to the 25-dB PAR were not retested.

In a second field study, workers that perform sandblasting operations for the Grand Coulee Dam were fit-tested using HPD Well-Fit^TM. The sandblasters’ exposures are about 130 dB peak sound pressure level, which allows them to perform sandblasting for less than nine minutes a day using the standard OSHA method for estimating worker noise exposure under hearing protection (50% de-rating of labeled noise attenuation). Using HPD Well-Fit^TM, NIOSH demonstrated that the workers received 30 dB or more attenuation from their protectors – far more than the estimate based on the OSHA de-rating scheme. Using this information allows the worker to conduct sandblasting for 2 hours a day, an obvious benefit for their employer. Furthermore, five workers involved with sandblasting were fit-tested before and after a work shift to demonstrate that the hearing protection was not shifting during their work. The second figure demonstrates the overall attenuations before and after a work shift and the change in attenuation between the two measurements.
NIOSH has licensed HPD Well-Fit^TM to Michael and Associates which markets it as FitCheck Solo* at www.michaelassociates.com/index.php/p/fitchecksolo

. NIOSH is working closely with HPD manufacturers, universities, professional associations, and testing laboratories to further develop and standardize HPD fit-testing technologies. In the coming year, we expect to complete an American National Standard for qualifying the performance of fit-test systems. This standard will ensure that all systems meet minimum standards for measuring hearing protector attenuation and calculate PAR in a uniform way. Rather than relying on the noise reduction rating posted on hearing protector packaging, workers and consumers can now measure the fit of their personal protectors. The future for hearing protection is fit-testing.
Captain William J. Murphy, Ph.D.; Dr. Mark R. Stephenson, Ph.D.; Captain David C. Byrne, M.S. CCC-A; Christa L. Themann, M.S. CCC-A
CAPT Murphy is a physicist and is co-leader of the Hearing Loss Prevention Team in the NIOSH Division of Applied Research and Technology. CAPT Murphy is an officer in the Commissioned Corps of the U.S. Public Health Service.
Dr. Stephenson is a research audiologist and the coordinator for the Hearing Loss Prevention Cross Sector Research Program and is a member of the Hearing Loss Prevention Team in the NIOSH Division of Applied Research and Technology.
CAPT Byrne is a research audiologist in the Hearing Loss Prevention Team in the NIOSH Division of Applied Research and Technology. CAPT Byrne is an officer in the Commissioned Corps of the U.S. Public Health Service.
Miss Christa L. Themann is a research audiologist in the Hearing Loss Prevention Team in the NIOSH Division of Applied Research and Technology.
*References to products or services do not constitute an endorsement by NIOSH or the U.S. government.