What Does Pinging Sound Like?

I'm killing time before work and it occured to me, I've never heard what "pinging" sounds like.
I looked on youtbube, and there is so much background noise on all the videos, I can't tell what is it.

" more of a plastic clattering sound. A ticking would be more accurate of a description before pinging. Not metalic at all. Someone above mentioned sounding like a small exhaust leak, more of that tone than metallic, marbles, pinging. "
"Does it sound kinda like popcorn popping and it happens at the same load and RPM? "
"the loose heatshield is a close description, but not metallic, more like a plastic snapping sound and from the drivers seat it sounds like it is coming from inside the dash"

Can anyone elaborate?
maybe post a specific video that would show it really well?