Some people are just always loud, and have to constantly be reminded to quiet down.
Little kids. In Pre-school through elementary school, kids are usually taught to use their indoor voices.
It's very common for people with autism to speak MUCH louder than necessary. Because of their lack of social savviness, they may not realize they are unintentionally shouting until this is pointed out to them.
Drill Sergeants in general.
Many DIs are actually fairly quiet when they're not "on", but it's pretty much a prerequisite for the job that you have the capability to embody this trope.
They generally get quieter as their trainees get closer to graduation and become a more cohesive group; but if you screw up, they will be more than happy to remind you that they still know how.
Hans Bauge, a popular Norwegian TV-debater in the 1990s.