On PTS the dragons don't "shout" most of their skills (for wild ones at least, haven't try the trial), there is only 2 occasions they shout ( one is the first word of unrelenting force shout, the other is 2 words of the firy breath shout I think), on other occasions (different type of fire breath, creature summons etc) they are just silent, don't shout and don't say anything in tamrelic language