I suspect it's due to people tensing their lower jaw in anticipation of a loud sound. I can do this at-will, and I hear something that I would describe in similar terms. I also triggered/heard it the first time I watched the animation (and I don't think I did it deliberately, although I was expecting it to happen).
My theory is that it's due to the jaw muscles vibrating when they tense, so an entirely physical sound conducted through the jaw/skull; rather than a neurological sound. I expect if you stuck a sensitive enough microphone in my ear, it would be audible.
Maybe this GIF is causing this reflex to fire. In the absence of the loud anticipated sound, your brain may be interpreting the flexing itself as a sound.
Comments
I suspect it's due to people tensing their lower jaw in anticipation of a loud sound. I can do this at-will, and I hear something that I would describe in similar terms. I also triggered/heard it the first time I watched the animation (and I don't think I did it deliberately, although I was expecting it to happen).
My theory is that it's due to the jaw muscles vibrating when they tense, so an entirely physical sound conducted through the jaw/skull; rather than a neurological sound. I expect if you stuck a sensitive enough microphone in my ear, it would be audible.
It may not even be tensing of your jaw.
https://en.wikipedia.org/wiki/Acoustic_reflex
Maybe this GIF is causing this reflex to fire. In the absence of the loud anticipated sound, your brain may be interpreting the flexing itself as a sound.
Yes. I expect that's it. I think the jaw tensing may be a side-effect of how I get that to happen.