Noise attenuation of earplugs. In Fig. 1.6 are plotted the experimental average and standard deviation REAT (real ear at- tenuation threshold: MADFop − MADFoc) obtained in diffuse field as well as the certified ANSI REAT (Industrial Noise Laboratory, 2007) (average ± two standard deviation and stan- dard deviation) for the Sonomax v3 S2/M2 custom earplugs. As can be seen in Fig. 1.6 the experimental REAT results are in agreement with the ANSI certification ones. As mentioned previously, the NR values were obtained before each experimental phase with occluded ears to check that the earplugs’ attenuation had not changed significantly between the two phases. The delta between NRcb obtained in the two experimental phases is presented in Fig. 1.7. At low frequencies there are practically no differences. At high frequencies the delta is slightly higher, but still acceptable, especially because the fit variability of earplugs is high at high frequencies. The small differences obtained confirmed that the subjects have placed their earplugs in the same manner during the two experimental phases. As the earplugs have −10 −20 −40 −50 250 500 2000 4000 8000 REAT [dB] std [dB] −× −
