This was a really recent realization for me.
I am one of the people who can voluntarily activate the tensor tympani muscles in my ears to create a low level rumbling sound. I recently tried explaining this to someone else and they still think I am making it up.
You are not alone! I have always been able to do that too. It still doesn't help with the tinnitus I've had since I was 4 or 5 though.
What was a revelation to me was the idea that everyone was only sleeping 3 or 4 hours a night. I thought I was perfectly normal in not sleeping for normal time spans. And despite the drugs and cpap machine I'm prescribed, I still can only sleep 5 or 6 hours now and often less. But I often am able to get to REM sleep now.
I use to control it before, but since I'm on some other medecine, it start to have its own will.
It happen to me unvoluntary like every 5 or 10s. That's SO FUCKING ANNOYING !!!
I can do this as well, as can one of my siblings and my father so I assume there is a generic component. Used to call it "ear clicking" since it is audible to others if they put their ear to yours in a quiet environment.
I figured out that was the name when googling about it some years ago.
Is it just a click or also the described rumbling. Because I don't hear a rumbling but I do make the clicks when I notice that my ears need to adjust to the air pressure.
If you hold it tense you get a rumble as described but the first time I tense it will make a little click. If I keep applying tension and release eventually it will stop clicking and just I'll just hear the rumble and it will take a bit to "reset" to where it clicks again.
Humans are weird.
Edit: I quick kagi search turns up a Reddit thread saying the clicking is caused by "Voluntary Opening of the Eustachian Tubes" which is equalizing the pressure in my ears. That sorta explains why it stops clicking after a bit.
I don't remember where I was made aware of it, but it was probably this. I used to listen to NSTAAF regularly. This fact probably just got buried in the back of my head until it had the opportunity to come out now.
Just to clarify, since I don't know if my experience is what you all are describing: this sounds kind of like what I hear if I start a yawn. Is the rumbling sound just for a second or can you make it indefinitely? And can you also make a short click or series of clicks?
I can get those sounds if I tense up some muscle(s) that you would also use to start a deliberate yawn. The clicks are easy to make, with less tension, and the rumble happens with more tension and it's only for about a second or so. Also I definitely hear the rumble during a yawn. Does that sound like what you mean or am I describing something completely different?
When you yawn sometimes you hear a little clicking noise in your ear canals, it's earwax coming into contact briefly and separating, you can do it voluntarily similar to rumbling but I need to open my jaw a little for that effect