A study of the real-world noise attenuation of the current hearing protection devices in typical workplaces using Field Microphone in Real Ear method.

Background: Actual noise reduction of the earmuffs is considered as one of the main challenges for the evaluation of the effectiveness of a hearing conservation program.

Objective: The current study aimed to determine the real world noise attenuation of current hearing protection devices in typical workplaces using a field microphone in real ear (FMIRE) method.

Methods: In this cross-sectional study, five common earmuffs were investigated among 50 workers in two industrial factories with different noise characteristics. Noise reduction data was measured with the use of earmuffs based on the ISO 11904 standard, field microphone in real ear method, using noise dosimeter (SVANTEK, model SV 102) equipped with a microphone SV 25 model.

Results: The actual insertion losses (IL) of the tested earmuffs in octave band were lower than the labeled insertion loss data (p < 0.05). The frequency nature of noise to which workers are exposed has noticeable effects on the actual noise reduction of earmuffs (p < 0.05). The results suggest that the proportion of time using earmuffs has a considerable impact on the effective noise reduction during the workday.

Conclusions: Data about the ambient noise characteristics is a key criterion when evaluating the acoustic performance of hearing protectors in any workplaces. Comfort aspects should be considered as one of the most important criteria for long-term use and effective wearing of hearing protection devices. FMIRE could facilitate rapid and simple measurement of the actual performance of the current earmuffs employed by workers during different work activities.