Inter-laboratory comparison of three earplug fit-test systems

Abstract

The National Institute for Occupational Safety and Health (NIOSH) sponsored tests of three earplug fit-test systems (NIOSH HPD Well-Fit™, Michael & Associates FitCheck, and Honeywell Safety Products VeriPRO®). Each system was compared to laboratory-based real-ear attenuation at threshold (REAT) measurements in a sound field according to ANSI/ASA S12.6-2008 at the NIOSH, Honeywell Safety Products, and Michael & Associates testing laboratories. An identical study was conducted independently at the U.S. Army Aeromedical Research Laboratory (USAARL), which provided their data for inclusion in this report. The Howard Leight Airsoft premolded earplug was tested with twenty subjects at each of the four participating laboratories. The occluded fit of the earplug was maintained during testing with a soundfield-based laboratory REAT system as well as all three headphone-based fit-test systems. The Michael & Associates lab had highest average A-weighted attenuations and smallest standard deviations. The NIOSH lab had the lowest average attenuations and the largest standard deviations. Differences in octave-band attenuations between each fit-test system and the American National Standards Institute (ANSI) sound field method were calculated (Attenfit-test - AttenANSI). A-weighted attenuations measured with FitCheck and HPD Well-Fit systems demonstrated approximately ±2 dB agreement with the ANSI sound field method, but A-weighted attenuations measured with the VeriPRO system underestimated the ANSI laboratory attenuations. For each of the fit-test systems, the average A-weighted attenuation across the four laboratories was not significantly greater than the average of the ANSI sound field method. Standard deviations for residual attenuation differences were about ±2 dB for FitCheck and HPD Well-Fit compared to ±4 dB for VeriPRO. Individual labs exhibited a range of agreement from less than a dB to as much as 9.4 dB difference with ANSI and REAT estimates. Factors such as the experience of study participants and test administrators, and the fit-test psychometric tasks are suggested as possible contributors to the observed results.

Hearing protector fit testing with off-shore oil-rig inspectors in Louisiana and Texas

“…Poorly-fit earplugs can enhance the stimulus signal and result in negative attenuations as well. From an inter-laboratory study that NIOSH conducted assessing the performance of HPD Well-Fit, a range of ±2 dB can be expected for the repeatability of a threshold assessment (Byrne et al 2016). Regardless of the cause, workers with obviously low attenuations were reinstructed and retested.…”

“…Over time, other fit-testing systems have been developed and studied for their performance both in laboratory and field environments (Murphy, 2013; Berger et al, 2011; Schulz, 2011; Byrne et al 2016). Microphone in real-ear (MIRE) measurement systems such as Phonak’s SafetyMeter and 3M’s EARfit Validation System require use two microphones measure noise reduction of a protector.…”

The viability of hearing protection device fit-testing at navy and marine corps accession points

“…In addition, the 3-freq test protocol has been shown to be in agreement with the gold standard REAT method. [18] On the basis of the current results, there is little rationale to support additional test frequencies beyond the three including in the 3-freq protocol used for this study.…”

“…Output from this system type, however, has not been as closely correlated with the other two system types and/or the gold standard method. [18] There are pros and cons to each system and system type. Regardless, the intent of all of these systems is to provide an individual assessment of the performance of an HPD on a given user in the field.…”

Hearing Protector Attenuation and Noise Exposure Among Metal Manufacturing Workers

“…Participants were tested using the Michael and Associates' FitCheck Solo (State College, Pennsylvania) REAT fit-testing system. This software program has been verified against ANSI S12.6-2008 (ANSI 2008) standards (Byrne et al 2017). The program was installed on a laptop and used a mousebased patient switch to measure participants' responses, and a sound-attenuating FitCheck earcup (TDH-49P) connected to the laptop with a 3.5mm electrical connector to deliver audible test stimuli.…”