A noise-cancelling earplug assembly (100) is provided, having an ear piece (110) for insertion into the ear canal and a housing (130) removably attached to the ear piece (110). A hollow core is defined in the housing (130) to receive a sound-selective sound barrier (132) that contains at least one sound filtering element to attenuate sounds reaching the ear drum. An end cap (1500 is provided and is attachable to the housing (130) to enclose the sound-selective sound barrier (132) inside the housing (130). The sound selective sound barrier (132) can be removed from the housing (130) of the earplug and replaced with a different sound selective sound barrier with different sound attenuation characteristics.
