Ratteling when accelerating?

Almost every time I accelerate, from a dead stop or while rolling in any gear, I will get this rattling sound that seems to be coming from in front of the driver's side firewall. I don't know if this could be the timing chain or not...it seems like it has been doing it more often though. It will do it whether the car is cold or hot. Any ideas on where this rattling might be coming from?

Thanks.

I should probably also mention this is an automatic and makes the noise going up/down a hill and on flat ground. Any ideas? Thanks.