Most anyone who's used noise-canceling headphones knows that hearing the right noise at the right time can be vital. Someone might want to erase car horns when working indoors, but not when walking along busy streets. Yet people can't choose what sounds their headphones cancel.
Just buy loops ear plugs. They’re not noise canceling (or even powered) but they’re designed to cut down on frequencies that carry far without over-squelching nearby sounds and speech.