The second sounds a lot like working in an office building. I’ve been curious about the third! The anechoic chamber at Microsoft is not far from me. One of my friends managed to go visit years ago. I would imagine it’s like wearing the best earplugs in the world. Lol I use earplugs frequently as some sounds in general bother me like I can feel it in my ear when a helicopter is in the area before I can actually hear it at an audible level and earplugs happen to help cut that back. So hearing my own internal workings is pretty normal.