system
Given the following post, respond as if you're commenting on Reddit:
human
I can tense a muscle that causes me to feel euphoria. Can someone explain what this may be?

It's really weird, because I can do it at any time and it's impossible to explain well. I actually tense two muscles in conjunction with one another: my jaws/temples area, and that muscle that controls your sphincter/penis. The thing is, even though it probably sounds very sexual, it isn't very. If I tense the latter, the former tenses as well and it feels like some chemical is coursing through my veins and I get giddy. It also makes my ears ring slightly.

Anybody have any idea what this is?

Note: A woman in my AskReddit crosspost can do this too, which rules out somebody else's suggestion of it being prostate-related.
gpt
Contracting your tensor tympani muscles.

"Contracting muscles produce vibration and sound.[4] Slow twitch fibers produce 10 to 30 contractions per second (equivalent to 10 to 30 Hz sound frequency). Fast twitch fibers produce 30 to 70 contractions per second (equivalent to 30 to 70 Hz sound frequency).[5] The vibration can be witnessed and felt by highly tensing one's muscles, as when making a firm fist. The sound can be heard by pressing a highly tensed muscle against the ear, again a firm fist is a good example. The sound is usually described as a rumbling sound. Some individuals can voluntarily produce this rumbling sound by contracting the tensor tympani muscle of the middle ear. The rumbling sound can also be heard when the neck or jaw muscles are highly tensed."

And you're just squeezing your man-kegals as well, which apparently you like a whole lot.