Unless in the case of immediate danger, raising your voice, especially with negative undertones is not necessary. The toughest teachers are not those that yell. In fact, training at high end horse shows is rather quiet. Projection can be relaxed and focused.
I am often amazed at how quietly keen horsemen can communicate. There is a technique to bringing volume way down, in order to talk privately amid others. It's a real skill, a social grace.
Everyone gets frustrated. But, I think to the point of whether to raise your voice, this is one of those areas where we do well to let the horses lead. They teach us that clarity and confidence drive effective change, not fear nor disrespect. That's sound horsemanship. Yelling out of your own frustration is a distraction to the goal at hand.
As I walk around shows, whether one responds best to a hard push or hand-holding, to me, raising one’s voice feels amateurish. It does not support a good feel for the horses. You can see it how the great grooms don’t get upset. Steady and clear. #bigheartswin ~Ruthann