Not sure when it happened, but the sound of dragons in my game have been muted, most likely due to a glitch.
Now, I'm running around Skyrim with the extra layer of threat a dragon can literally land on top of me and I won't know it. At first, I thought "WTF", but now, I'm actually loving this aspect of the game, giving me a sense of true danger.
The first time it happened, I was fighting a few Forsworn and turned around to be on my merry way and it was right there. I literally jumped as I saw it, because I didn't even know it was there.
The second time was near Whiterun. Thing just landed inches in front of me. Poor thing. Didn't stand a chance.
The third time was the best. In my favorite Dragon Rest capital of Skyrim, aka Morthal. I was walking between two buildings and walked right into the back of one. I laughed, and thought "What's he doing here?" As I was engaged with this one, another showed up, just as silently as the first.
Here's hoping that, if TES VI has dragons, they stay stealthy.