Welcome to Just Commodores, a site specifically designed for all people who share the same passion as yourself.
Was driving on highway many years ago, unknowingly drove over an object that was thrown up against underside of car and pierced the floor r/rear passenger foot -well. Thankfully no one injured. Point is that the noise, cause by about half a length of flat spring (probably off a truck) that upon contact made a hell of a loud bang. Have a look underneath your vehicle for such evidence.