Why do people talk so loud?? Seriously. Can you just lower the volume a bit? It sounds like you're trying to talk to someone on the other side of a train station. It sounds like you're trying to talk to someone while a metal band is performing.
I find if you talk at a lower volume people will actually make more of an effort to listen to you. If you talk softer, people won't try to talk over you. They'll actually lean in and listen.
Maybe instead of trying to talk over who ever you're talking to you talk softer or-- GASP!-- you stop talking and listen.