Evaluation of commercial systems for the individual test of the hearing protectors’ effectiveness.

The average sound attenuation of hearing protection devices (HPD), established on a panel of test subjects, using a subjective standard method under ideal laboratory conditions, only allows comparing with regards to their labeled value.
Numerous studies have questioned these values which led to the concept of PAR (Personal Attenuation Rating). It appears that the only way to assess the effectiveness of a protector for an employee is to require an individual measurement of that protector for this employee.
Thus, recently, new systems that allow measuring the efficiency of a HPD for an individual, in order to assess the attenuation provided individually to the user, are now on the rise.
This paper shows the results of a study that inventories the existing systems and analyses the methods used by these systems. Four commercially available systems were tested to evaluate the performance of two ear muffs, 4 pre-molded or foam ear plugs, and 2 custom molded earplugs for 22 test subjects. The results were compared with attenuation obtained from subjective standardized measurements reinforced by the results obtained with of a standardized objective method.
Three of the four systems provide average attenuation close to the labeled values. For these three systems, the individual comparisons are acceptable in terms of global values, although the differences with the labeled values may be important. Therefore these systems can be effectively used to validate the selection of a HPD, especially for custom molded ear plugs, as long as uncertainties are taken into account.