Originally Posted by Fish
I spent time doing some acoustical work for a product we were developing. I can say for certain that being in rooms with the ability to efficiently absorb sound are annoying. It's hard to explain, and it may be different for everyone, but it was as if there was pressure on the eardrum. I suspect this sensation was due to the fact that the eardrum wasn't vibrating at all. Weird stuff.
Actually, I believe you not only hear your heartbeat, but the blood flowing through your veins.