Preferred Methods for Measuring Hearing Protector Attenuation

There are numerous well-documented measurement methods available to evaluate hearing protector attenuation, however, some are flawed or difficult to implement and some can and have been misused with the erroneous results fostering misleading conclusions. This paper will examine the three most robust methods including the “gold standard” in hearing protector attenuation measurements, namely real-ear attenuation at threshold. It will be compared to the most useful alternatives such as microphone in real ear, including the use of probe microphones, imbedded microphones, and miniature microphones, and to measurements using acoustical test fixtures, also called blockheads. Examples of the latter include the ANSIand ISO-specified blockheads, KEMAR, and others. Illustrative data will be provided to guide the user in the application of such techniques and tools, and to point out errors to avoid. None of the three methods is entirely “accurate,” all being plagued by various experimental artifacts. However, REAT has been thoroughly “road tested” and standardized around the world, and has been shown to be the most accurate at estimating the performance for a defined group of subjects under a given set of conditions.