Listening with the aid of headphones was at the heart of the early radio culture of the 1920s. After those years, however, earphones became the exception as loudspeakers became the norm. For quite some time thereafter, the wiring of hearing was limited to the use of monaural earbuds in situations where the use of loudspeakers would have disturbed others. In West Germany, the binaural headphone started to make a comeback in the late 1960s due to the growing fragmentation of family life along with the widening range of electronic leisure possibilities and the rise of hi-fi culture. It was only at the end of the twentieth century, however, that binaural headphone listening emerged as the dominant culture of listening and caught up with the burgeoning mobile urban life style. Taking the case of West Germany, this article asks: What is the impact of ear-wiring on social life? And, what new kinds of perception result from headphone listening? It traces how the use of earphones turned from being a static "technique of listening" into a mobile "technique of acoustic privatization." Ultimately, this article interprets today's portable headphones as "head cocoons" that enable mobile listeners to actively carve out sonic privacy while on the move.