I can do something similar but its like a deep humming sound almost exactly like wind is passing your ear and I can do this for 40 seconds
Not sure if this is at all linked, but i noticed that when i stopped consuming aspertame, the urge to compulsively flex this muscle stopped. maybe it's completely unrelated, but it's been a few months now and the urge still hasn't resurfaced. I'll post an update after a few months.
Not the same as "popping" open your eustachian tube. Instead you are just creating the sensation of a rolling thunder sound, not a thunder clap, which might have lead you to think this was ear popping. Ear popping is usually produced by swallowing or chewing. The noise being talked about here is produced by tensing the muscles around your ears, such as pulling your ears back with these muscles. I've been able to do it for as long as I can remember. Never met anyone else who could.
+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.