clk 320 "chirping"

[richard28]

I'm trying to figure out where this sound is coming from. Chirping, just like a bird, occurs during driving, over bumps, over smooth surfaces and even can be heard when I close the front doors on both sides of the car. Thought it might be the serpentine belt, but it seems tight and in good shape. Recently replaced front & rear shocks, rear springs (left one cracked) and ball joints; tie rods are leaking & will be replaced next week. Thanks for your thoughts.