The Combat Arms earplug is a dual-ended, non-linear, selective attenuation device with one yellow and one olive end. If the olive end was inserted into the ear in the “closed” position, it was supposed to block all sounds, like most standard earplugs. If the yellow end was inserted in the ear in the “open” position, it was meant to block only higher-decibel noises like explosions, while the wearer could still hear normal-volume noises like conversation. This feature was very appealing to the US military, as it meant that soldiers could communicate with each other, hear and respond to commands, etc.
The Dual-Ended Combat Arms earplugs sound like a good solution, but Moldex’s lawsuit asserted that design defects in the plugs caused them to loosen, removing the ear protection they were meant to provide. The earplug stem was not sized correctly, so it couldn’t be placed deeply enough in some ear canals. For those wearers, the outer end of the earplug could press into the ear canal and revert to its uninserted shape, disrupting the protective “seal” the earplug was supposed to create. This left the user vulnerable to hearing damage and with no way to know the device had failed as there were no apparent signs.