2001 Buick Century Whining noise from engine while acceller

Thank you for your time. A while back, I was at a stop, and as I accelerated (rather quickly) I heard a "ping" sound, literally like you would hear when a metal driver (club) hits a golf ball come from under the front of the car, and from that point on, here and there, my engine would kick as I would move from a standstill, feeling like the transmission was in neutral for a moment where it kind of rolls, and then it kicks into gear. Now interestingly, a few months later, that doesn't seem to happen any more, but what I am noticing is a sound coming from somewhere near the engine area; a whining sound like that of an infant moaning/crying as I step on the gas pedal usually after driving for 10-15 minutes, and consistant on freeways above 55 mph, but only while accellerating. If I let go of the pedal, the whining quickly stops in about a second. It could be my imagination, but it feels like the acceleration is a little "shallow" almost like I'm driving with a parachute tugging ever so slightly at my car. The reason why I mention both these symptoms is because of the possibility they my be linked(?)