When equipment for head protection is combined with that for hearing protection, the head band of
ear muffs may prove incompatible. For a combination of equipment for head protection and hearing
protection, ear muffs attached to the industrial helmet can be used.
Helmet straps might break the seal of the attached earmuffs if they were not designed to be compatible.
References to the German technical rule DGUV Regel 112-194 governing the use of hearing protection, January 2015 (in German):