This standard pertains to systems intended to estimate the attenuation of hearing protection devices (HPDs) obtained by individual wearers in actual practice. Such systems are designated field attenuation estimation systems (FAESs). This standard provides a classification of FAESs and specifies performance criteria. It also details the evaluation methodology and statistical calculations to be performed on such systems in order to state the uncertainty associated with the individual attenuation estimates that they provide, and specifies a method for computing a personal attenuation rating (PAR). FAES-derived data do not replace the attenuation values from ANSI/ASA S12.6 or the insertion-loss data from ANSI/ASA S12.42, nor are such data suitable for labeling the attenuation of HPDs.