I don't claim to know what that is, but I've been interested in it for a while.
When I trip, read "trip" loosely, it's really strong. It's a kind of rush up my spine that "condenses" with a roar in my head. As some others have mentioned, squeezing the third eye (big smile, scrunched eyebrows, raised ears) helps it "condense."
I did a big one right now. Ha!
Once I took a 15-minute nap and dreamed of an old man who was telling me something in rhyme -- I forgot the rhyme on waking, but the gist of the message was "always keep the roar in the back of your head, and you'll be ok."
I think it might be an awareness of what the yogis call prana. It's definitely something that accompanies deeper awareness.
Watch out if the "beat" happens on its own. Happened to my brother once while bicycling and he felt the need to slow down, narrowly missing a car wreck just ahead.
If you "squeeze" your eyebrows, face, ears, as described and get colored visual effects, let me know. I'm still wondering about those.
If you want to develop it, check out nada yoga -- sound yoga.