What does engine ping sound like?

I am pretty mechanical inclined but never heard a engine ping, I have heard spark knock but thats it. I have a 98 dakota 5.2 v8. Mods exhuast,CAI,sct tuner. I just got this tuner last week and have been messing around with different settings. Well I have it on the 93 tune im running 87 and 89 mixed(40/60) Just too see if I would get ping(oh also still a 190stat but 1 range colder plugs) Today I noticed a weird sound coming from my truck couldnt hear it too well then later on when I was driving with my windows down I heard it real good sounds like a exhaust leak. Then I started thinking could this be engine ping? I didnt have time to check my headers tonight to see if they are leaking but I did notice the noise is most noticeable when the truck is lugging, maybe its louder cause the rpms are lower and my exhaust isnt as loud. Some one please try to explain this ping noise to me. Oh and I dropped my tune down while on 89 gas and still that noise it there. Ill reset it back to stock and see what happens worst thing is ill have to put in a 180 stat and maybe 1 range colder plug. Or maybe it is a exhaust leak which I am not looking forward to fixing!