Abstract: An enlarged earcup which occupies substantially all of the helmet eardome and provides greater attenuation of ambient noise, especially low frequencies. The speaker and earseal are mounted onto an adjustable assembly. The assembly is slideably mounted onto a flange which extends inwardly from the earcup's rim. The assembly includes a pair of parallel annular plates which sandwich the flange therebetween.

Abstract: A sound-attenuating impact-absorbing earcup comprises a shell having a plurality of generally circular recesses adjacent to the periphery of the cup which function as stiffening contours. The stiffening contours increase the effective stiffness of the earcup shell, improving its sound attenuating capability, and also concentrate applied stress onto those portions of the stiffening contours nearest the point of applied stress. Sufficient applied force causes the shell to fracture in the areas of the stress concentrators, thereby to absorb impact energy in a controlled manner without transmitting it to the head of the wearer. To further enhance its sound-attenuating and impact-absorbing capabilities, the earcup is formed of a low-tensile-strength, high-elongation, high-loss-factor material such as polyvinyl chloride or similar polymer.

Abstract: An arrangement in which a toggle mechanism on the outside of a proective helmet acts on an end of a nape strap outside the helmet to shorten the effective length of the nape strap within the helmet to move the wearer's head forward to bring the wearer's face into engagement with the face seal of a face mask attached to the helmet.

Abstract: A protective helmet assembly in which a manually operable pump carried by the helmet outer shell is accessible from outside the shell to inflate two inflatable bodies disposed between the shell and respective sound-attenuating earcup subassemblies suspended from the shell adjacent to the wearer's ears. An element accessible from outside the shell can be actuated to deflate the inflatable bodies when the helmet assembly is doffed.