1998 Mercury Mountaineer-'pinging' sound from..?

shecraftsetc

I have a 1998 Mercury Mountaineer. Yesterday evening it started making a 'pinging' sound from what sounds like the drivers side. It noise is regularly "rotational"--in other words, as you speed up the noise remains regular...but faster...and conversely when you slow down, etc etc. Any ideas?

PF_Flyer

From a wheel area? Not the engine?