I'll start by saying I don't think it's a hearing problem, as she uses a normal voice in non-excited conversation, and can hear questions asked to her in a normal voice (aside from what I suspect is normal tuning-out of my voice...)
When my daughter is in situations where she's excited, she frequently yells at a volume that's way louder than appropriate, given her proximity to other people. It sometimes happens when we're in groups, playing outside, or if she's watching TV and she wants to tell me about something she saw that she really liked. As a specific example, I was helping her off the swing today and her sandal fell off - she shouted "MY SHOE!!!" right in my face as it happened. It comes out sounding angry, though I'm pretty sure that's not intentional - it's just really loud.
I know it takes time to learn what's appropriate for a situation, but when can I expect my child to start using an appropriate volume when speaking in excitement? I feel like I'm constantly asking her to speak more quietly, and constantly giving reminders, but any improvement is minor at best, and it usually only applies to her current thoughts - the next time there's an exciting situation she's back to yelling.
Is continual reinforcement and reminders the best approach here? Is she too young to understand the concept at 5, and I should just relax? I feel like I'm constantly shooshing her, and it's not my intent to curtail what she's saying, but sometimes my frustration manifests itself as stopping her speech rather than adjusting her volume, so I'm hoping for a new approach.