I hear a hollow metal banging sound when driving my 97 explorerm does anyone have any ideas?

Does the sound increase ...like knocking faster with engine speed, the higher rpm the faster the knock? And loud or subtle? And mileage on engine?

I know if a baffle breaks loose inside of the muffler it can sound like that but like FordNut ask does the sound change with engine speeds.

thanks for response, no actually the sound bangs loud and then it will quit the faster you go but it sounds like something is going to break mileage is 199000

Check and see if a lug came off and is banging around inside the plastic cover which covers the hub and five lug nuts. Sounds like the condition is centrifugal force related. If something came off which moves in a circular direction, the outward force would pin the object to the outer limits of the cavity. Question: Is the sound present when the vehicle is stopped-mot moving and just idling?