it was a dragon now i know what you are thinking "i said im not doing the main quest you dolt" but maiq has told tales of invisible dragons that live very high up in the clouds. and that it flew off at an incredible speed high above you creating what is commonly known as a sonic boom invisble dragons are speculated to be far different from the Dovah for they are believed to not be sentient and well they are invisible....or so M'aiq has told me when i asked him about your tale. yet he also warned the dwemer could have returned and that if you hear heavy metallic footsteps outside your house and hear a knock at your door do not open it for it is the dwemer inquisition!

Maybe it's sort of an easter egg related to upcoming DLC or expansion ... or not. Are there any glaciers in that area? I've heard them make some pretty loud, frightening sounds -- admittedly, only when I'm all up in their territory.

Outside of Whiterun I have experienced a low, growling like rumble that lasts as long as I stand over its source, but I'm not sure what it is.

Nope. it's in the Reach. no glaciers.
That is the sound that bats make in caves. it's a glitch.

PC or Console?

If Console did your controller vibrate? If so it was an ingame event, likely a dragon, check nearby NPCs for a dialogue along the lines of "Hey where did that Dragon go?"

I did see somewhere talk of this being a bug on the console, but all I've found is confirmation it isn't a bug.

Get Pete on the horn! PETE TWEET!!!

This might turn out to be like the noises appearing all over the world on youtube... except it's now earthquakes.

I've experienced this too. It's similar to a dragon landing, but a little different somehow. Feels like an earthquake. The controller vibrates, so it's an event (not a camera glitch). Probably a bug, that's my guess.

This character hasn't done any MQ quest since unbound so it's not a dragon. though on other characters who have and haven't done the MQ quests it still has made the noise.

Could be a bug that somehow triggers the "Graybeard summoning you" screen quake prematurely...

Twas Argonian cooking. J'rahzir knows. The swamp gases are cooked within such pastries. Then such gases meerly build up and bring terror to all who is around. J'rahzir remembers his first experience with one who experienced such cuisine. He hid... and cried...

samething in the sameplace happend to me. weird. no sign of anything that could have cased it.