A combination of equipment for eye/face protection and hearing protection may significantly reduce the sound
attenuation properties of ear muffs, for example owing to thick goggle sidepieces. Measurements
conducted by the IFA revealed that thick goggle sidepieces reduced the sound attenuation by up to 14 dB.
In other words, the exposure to sound pressure was up to 25 times higher.
References to the German technical rule DGUV Regel 112-194 governing the use of hearing protectors, January 2015 (in German):