It comes with experience, you don't have to be loud to take control of anything including a scene. Matter of fact the loud ones will usually be tuned out. Your service should be allowing you to learn from more experienced providers. Stay calm, make eye contact, be deliberate in your actions, you don't need to raise your voice, the more confidence you exude that you have control over what's going on the more confident other providers and the patient will have in you. This comes with seasoning. One of the most overlooked aspects of this job is controlling chaos, you don't have to be yelling, screaming and running around like a chicken with his head cut off to achieve it. Smooth, level headed approach, know the aspects of your job and how too relate them to your patient and soon people will be looking to you to run the show.
Good luck.