+1 for jacjack's answer. I was about to comment that opening of the eustachian tubes is completely different than making the 'thunder' sound. When you open the eustachian tubes while humming, the hum becomes very loud internally. You can feel your ears "open" up and while holding them open and breathing, you can hear and feel the air coming through the eustachian tubes. When you make the 'thunder' you can make it anywhere from soft to loud (the silent beat-boxing to onesself when sitting alone) doesn't 'pop' your ears at all...or at least not mine ;) i can do both ears simultaneously...to be able to do only one at a time i have to press my jaw to one side or the other (esentially blocking the eustachian tube on the side that i move my jaw to). i never really thought this to be a weird thing; i just assumed everybody could do it. i was searching for skipped heartbeats when yawning tonight and happened to ask myself, "what other weird thing can i look up tonight?" lol. this thread was enlightening to say the least, so thank you all :)
Some useful references so far:
http://en.wikipedia.org/wiki/Tensor_tympani_muscle
The 'rumbling' noise arises from the straining of the tensor tympani muscle in the ear. If you stick a finger in your ear and grip the other fingers tightly, you can hear the same 'rumbling' noise from the exertion of hand muscles.
https://en.wikipedia.org/wiki/Ear_clearing
The ear clicking is the voluntary opening of the eustachian tube in the ear, a useful trick for scuba divers. You can record your 'clicking' with the phone against your ear.
https://en.wikipedia.org/wiki/Autophony
"When the Eustachian Tubes are deliberately held open, one's voice sounds louder in one's head than when they are closed." That's 'Autophony'. Useful for checking and pacing my breathing when jogging. And now that I'm into meditation, handy for focusing on my breathing during meditation, like putting on earphone without the music but less than using ear plugs.
I always know it's an uncommon ability because I have not came across any reference to it in my 48 years of existence but then the human body has many quirks and peculiarities, so wasn't unduly concerned. Arrived at this site because I was trying to find out if anybody is using it for breathing meditation but prior to that, need to solve the life long mystery of what it really is first. Glad I checked !
I too have been contracting this muscle voluntarily, but compulsively, particularly when I'm stressed or talking to someone and I'm nervous. Even when I'm not nervous, I'll still go through stretches where I compulsively flex this between 5 and 10 times a minute for about 400ms or so. If I concentrate on not flexing it, I'm fine, but I usually revert to this unusual behavior subconsciously.
Wow, I've been able to to this since I was a kid (I'm 50 now)! I never knew it had a name or that only a small percentage of people can do it. I found this forum because I have a small popping noise in my left ear when I do this for the past few days. I'm going to make a Dr appointment because the pop sound isn't going away.
Like many of you I can make my ears pop at will, but I hope someone is familiar with another manifestation. I can't remember when this began. When getting my eyes examined and they shine a bright light in my eyes I hear that thunder noise. It has also happened on occasion when going out in bright sunlight without sun glasses. It surprised eye doctors when I mentioned it. They speculated it might be caused by a head injury many years ago. I always though it was something everyone experienced.
im currently 29, I've been able do this ability my entire life, I can do it for as long as I like, it seems to raise my temperature. I've done it for hours on end just to see what it would do, after a few hours it turns into a crackly sound, I can make it as quiet or as loud as I require ,I can talk, read and listen and still do this, when my ears need popping I do it, I usually do it when I want to turn out, it all helps my imagination.... like going to la-la land, good to know there are other out there that can do it.