Charles W. Nixon
Armstrong Lab., Crew Systems Directorate, 2610 Seventh St., Wright--Patterson AFB, OH 45433-7901
The variability of the data measured in the WG11 interlaboratory study was compared with that measured in three other interlaboratory studies conducted in this country, in Europe, and in the Scandinavian nations. All studies utilized a real-ear attenuation at the threshold measurement paradigm and basically followed the procedures described in the current ANSI and ISO hearing protector measurement standards, with one major exception. The WG11 study utilized naive subjects and hearing protector fitting procedures that were relatively free from experimenter influences instead of the trained subjects and the ``best fit'' procedures required by current measurement standards. A subject fit (only hearing protector manufacturer's printed instructions handed to the naive subjects) and an informed user fit (manufacturer's instructions plus experimenter general comments to the naive subjects only relative to the instructions) were utilized for the WG11 study measurements. Comparisons indicate that the variability of the data collected under the less rigorous subject and fitting procedures of the WG11 study is at least equivalent to that measured in the other interlaboratory studies.