I’ve noticed the same thing. The audio mix from RNC official feed cuts out most of the crowd noise. It sounds a little better tonight, but the first two nights it sounded like they were in an empty warehouse.
This is not new. I noticed this in previous conventions. Democrat conventions sound intense and exciting and Republican conventions sound empty and dull. It’s lack of crowd noise. I wonder if it is on purpose. They are picking up p[odium & band feeds and that’s it. The crowd noise you hear is probably from the podium mike. Just my guess.