Observation on the variability of fitting by two experimenters at REAT and the agreement with objective measurement on three premolded earplugs

Abstract

Real ear attenuation at threshold (REAT) has been recognized as the gold standard method to evaluate the attenuation of hearing protection devices (HPDs). It has been standardized in ANSI, ISO/EN and AS/NZS documents. The fitting of HPDs is one of the key factors of REAT measurement. The experimenter fit protocol of ANSI S3.19 is considered one precise approach to obtain the “best fit” of HPDs. A study of the attenuation obtained between the three fits for two experimenters on the same ten subjects on three premolded three-flange earplugs was conducted at 3M E-A-RCAL laboratory, including two models of Chinese brands earplugs and 3MTM E-A-RTM UltraFit earplug. Good agreement was shown between the REAT results that were obtained by the two experimenters. The REAT result of one Chinese brand earplug shows much higher variability within subjects. Comparing with the insertion loss (IL) measured by G.R.A.S 45CB, which has been corrected for bone conduction, occlusion effects and physiological noise, produced IL for two of the tested earplugs that did not showed good agreement with REAT results at most, but not frequencies. The discrepancies will be discussed.