A method for forming a device (10) that fits into a person's ear canal, that carries sound from a pipe (B) of a speaker assembly (A) into the person's ear canal, and that blocks environmental noise. A first elastomeric material (14) is molded around an elongated core (16) to form a device body (12) with an outer surface that can seal to a person's ear canal. In one method, the first elastomeric material of the body is a soft foamable material and the core is a previously-formed tube (16) of a stiffer second elastomeric material, with the body bonded to the tube by being molded around it, either in a mold cavity or by extrusion through an extrusion head. In another method, the elastomeric material of the body is a non-foam, and the core (96) is a rigid pin that is removed from the earplug body after the earplug body has at least partially solidified.