Suggested standard hearing protector attenuation function relating to the NRR.

An assumption was made that a hearing protector (HP) attenuation function derived from some combination of the A-weights and C-weights used in the calculation of the NRR would produce a minimum difference between the NIOSH long R-value and the NRR-dBC + dBA + 3 (RNRR), regardless of the spectrum of the noise. Four hypothetical HP attenuation functions were derived. A mean R-RNRR difference, standard deviation and range were determined for these functions and for five real HP functions using 262 noise spectra. The mean R-RNRR difference for one of the hypothetical functions ("ED") was zero, with a standard deviation of .2 dB and a range of 1.6 dB. It was concluded that an HP designed to match the "ED" attenuation function would minimize the R-RNRR difference, regardless of the noise spectrum.