User blog comment:Omega natsu2/Chapter 352: The Flame's Voice, Predictions./@comment-3075024-20130915180836/@comment-7418318-20130915190406

So we aren't allowed to discuss the theories and go deeper into the details? That'd be only half the fun.

There are after all possibilities for them hearing it's voice despite the flame's physical absence, like it being linked with the place somehow or someone pretending to be the flame's voice.