Earmuff efficacy in the workplace using F-MIRE - a case report.

Purpose: To determine the field efficacy of an earmuff used by the employees of a private company.
Methods: Measurements were performed using a double-channel noise dosimeter. Noise levels collected in one-third-octave bands were corrected with the frequency response for diffuse sound field and attenuation was compared with values provided by the manufacturer of the hearing protection device (HPD).
Results: Comparisons between the corrected noise reduction and the attenuation provided by the manufacturer of the HPD show no statistically significant differences in attenuation for most frequency bands, with higher mean values for the observed corrected noise reduction. However, despite the fact that the field attenuation values are above those obtained in the laboratory, when individual attenuation values were compared with expected attenuation values it was found that the employees have below-expected noise attenuation in all frequency bands.
Conclusions: The fact that over 60% of the employees had frequency band attenuations below that expected for most frequency bands underscores the need for individual assessment of attenuation provided by the HPD in the workplace, to assess whether the HPD is functional and what provisions should be implemented in a specific workplace.