Attenuation of earplugs worn in combination with earmuffs.

If the attenuation that can be provided by a single hearing protection device (HPD) is inadequate for a given noise exposure and if noise control procedures are impracticable, the only remaining alternative is to use dual protectors, i.e. an earplug plus an earmuff. Such a combination can provide additional protection but it has long been recognized that the resultant noise reduction falls short of the algebraic sum of the attenuation of the individual devices1. This EARLog, #132, examines the utility of combining HPDs and suggests generalized guidelines for the description of their performance.