earphone
An earphone is a tiny device that locks you into your own world with chains of music. It grants the right to ignore others and acts as a barrier against human interaction. The louder you play it, the more invisible you become, eventually missing even the nastiest remarks about you. It masquerades as a professional shield for concentration on crowded trains, but in truth it stages an escape. Ironically, it frees you from external noise while isolating you from all social sound.