Noise from under truck

[sothunter]

I have a 2005 Ranger 4x4 4.0 litre engine. I began hearing what sounds like a rattle from under the Truck, the sound is similar to the noise made by a chirpping idler pulley. I notice it when hitting bumps in the road but its not the suspension because when the truck is parked i notice it when I close the Doors. Has any one else had this problem? Please Advise

 

[swamprat]

Maybe the heat shield on the cat. I had two come loose