I find with my active noise canceling phones it works best to play a white noise track in the background. The white noise track ensures that even during the gaps in the music or periods or low volume that I don't get distracted by conversations.
I just discovered this entirely by accident, because I grew tired of killing sox every time I played another audio source (and restarting it afterward).
Also, turning off the white noise is very uncomfortable once you've become accustomed to hearing it all the time.
