At a major hazard facility, sporadic cases of occupational noise-induced hearing loss have occurred despite the use of hearing protection devices. Preliminary testing with a system for measuring personal attenuation ratings (PAR) suggested that earplugs may not achieve the attenuation implied by their Australian Class designation in eld-use conditions. We believe that ours to be a world-rst study at the time it was conducted to check the relationship between Personal Attenuation Rating (PAR) and the Australian SLC80 classi cation for hearing protection devices, and the ndings can be used to complement studies based on the American Noise Reduction Ratio (NRR). Methods:A cross-sectional study was performed with 65 volunteers. Participants were recruited from Operations and Maintenance Technicians at the major hazard facility. The participants had their PARs checked with different earplug types using the 3M TM E-A-R t TM system. An earplug is deemed to have achieved a 'pass' if it achieved 22 dB attenuation for 80% of users (the de nition for Australian Class 4 hearing protection) Results :None of the earplug types achieved the attenuation implied by their class rating when tested in eld-use conditions. There were statistically signi cant differences in the frequency of achieving a 'Pass', and in PAR, depending on earplug type. Roll-down foam earplugs may provide superior attenuation compared to pre-moulded earplugs. Conclusion:Earplugs are unlikely to achieve the attenuation found in laboratory conditions during eld-use.Personalised selection of hearing protection devices based on t-testing results should be encouraged. Key MessagesThe relationship between PAR and Australian SLC80 Class rating is consistent with what has been observed in the rest of the world when comparing PAR with other hearing protection device classi cations such as the American Noise Reduction Rating (NRR). HPDs underperform in eld-use conditions compared to laboratory ratings.

Introduction:At a major hazard facility, sporadic cases of occupational noise-induced hearing loss have occurred despite the use of hearing protection devices. Preliminary testing with a system for measuring personal attenuation ratings (PAR) suggested that earplugs may not achieve the attenuation implied by their Australian Class designation in field-use conditions. We believe that ours to be a world-first study at the time it was conducted to check the relationship between Personal Attenuation Rating (PAR) and the Australian SLC80 classification for hearing protection devices, and the findings can be used to complement studies based on the American Noise Reduction Ratio (NRR).Methods:A cross-sectional study was performed with 65 volunteers. Participants were recruited from Operations and Maintenance Technicians at the major hazard facility. The participants had their PARs checked with different earplug types using the 3MTM E-A-RfitTM system. An earplug is deemed to have achieved a ‘pass’ if it achieved 22 dB attenuation for 80% of users (the definition for Australian Class 4 hearing protection)Results:None of the earplug types achieved the attenuation implied by their class rating when tested in field-use conditions. There were statistically significant differences in the frequency of achieving a ‘Pass’, and in PAR, depending on earplug type. Roll-down foam earplugs may provide superior attenuation compared to pre-moulded earplugs.Conclusion:Earplugs are unlikely to achieve the attenuation found in laboratory conditions during field-use. Personalised selection of hearing protection devices based on fit-testing results should be encouraged.