I'm getting a noise when I acellerate from a stopped position. When I'm stopped and rev the engine no noise also it doesn't sound like the brakes so I'm just trying to figure it out. It began to happen after I added refrigerant to the ac ac system but the noise happens with the AC turn off? Any help would be appreciated.

 

I thought it was AC related but it wasn't. Took it to a mechanic and he said an exhaust sheild was the issue he cut some off and all is fine

 

Those are commons. I have also seen noise developing due to aging of exhaust pipe gasket links. Some people replace those with all copper seals