My car has a knocking noise, more noticeable in the car on start up and driving slow but no knock at higher speeds. Seems to be louder when turn a/c on. Any suggestions?

Also, my front wheels sound like they are rattling only when going over imperfections in the road, no on large bumps or anything. I had new shocks and struts placed and still the same. Took it back to the shop they put it on lift and said might be brake calipers rattling??? Help!

 

Calipers could be. I greased the pin and rubber case and it noise went away for several months. Returning now after several months.