Thread: loud knock while accelerating that increases with speed

while driving my 06 grand prix started knocking loudly (no ping, loud knock). the knock increases in speed as I accelerate (like a card in bicycle tire) its kind of like I can feel it in the accelerator pedal as well. it only happens while driving is fine giving gas while parked. Does anyone have any ideas? my catalytic converter is in rough shape as well if that helps? connected problem?
ty for any possible assistance