I am not saying intense emotions universally result in yelling, but people very rarely whisper when say calling 9/11. Even just kids playing tag get lauder.
People normally get mute in stressful situation. They normally have troubles to express things, they talk in weak voice, whisper or not at all. They have one word answers to complex questions. And anything in between. Some dissociate and act normal or follow normal script by routine.
They don't whisper to the phone, they will put more conscious effort to talk into 911 call ... or the shaken mute person won't be the one making call.
You seriously never had to ask people to talk louder in noise environment? The "people yell" assumption is artifact of movies, not reality.
Asking someone to speak lauder in a noisy environment is normally because they aren’t raising their voice enough rather than them failing to raise their voice at all. It’s not easy to judge how laud you need to be but the basic feedback of failing to hear your own voice if you don’t speak up prompts raising your own voice.
As to going mute, some people do completely shut down in an stressful situation, but that’s associated with for more than their voice. I have no issue with an actor in a war movie endlessly stacking ammo from point A to B. But if their having a coherent conversation, activity and productively responding to stimulation, that’s very different.
I am not saying intense emotions universally result in yelling, but people very rarely whisper when say calling 9/11. Even just kids playing tag get lauder.