Not to continue to derail, but cast members are indeed allowed to yell under specific circumstances. Many attractions have specific guidelines on what predetermined spiels can be said over PA systems, and addressing a specific guest or party to follow directions with a PA is almost always an instant violation in non-emergency situations. In theatre shows this often manifests as the, "move all the way down," but you'll often see it on flat rides for a, "remain seated." Raising your voice is required to be heard over a noisy environment or ride system. Point being, there is a distinct difference between yelling for safety/efficiency and yelling rudely.