I can't block my nose in that way. I tried when your comment came in, but I can't conceive of how to do it.
With the ear popping thing, I just hear the rushing of my breath. I can see how you might be able to hear your heart. I might be making this up in my head, but I feel like maybe I could hear it when I was younger.
Wait a minute. If I hold my jaw right, I do get a very short rumbling apart from my breath. Is that what you guys mean?