engine sound from "vvvvv" to "thththththth"

[wwjd]

I AM FAR FROM MECHANICAL. Haven't even removed covers to see my engine yet.

But, got new plugs put in months ago... could one be bad or a wire come lose, and can I actually check it myself?

I'm pretty sure the engine used to have a smoother "VVVVVV" sound, and now it kinda sounds like a piston is missing or weak, "ththththththth" (tongue bouncing around in mouth).
Still kinda smooth and seems to drive fine.... MAYBE less power? hard to tell.

Ideas, for a not mechanic type with an open Saturday to poke around?

No, I don't have one of these plugin diagnoser things yet