When a person tries to explain a noise they hear on their car, they normally describe it as a knocking sound. The following could be the source of such a problem:-
1. Transmission mount or any other mount broken (check all of them). 2. Drive shaft. 3. Flywheel screws could be loose. 4. CV joints. 5. A loose bolt that is rattling and requires tightening. 6. A nut, bolt, screw, washer or something loose inside the door, or under the floor, engine bay or somewhere. 7. Stone, screw or bolt stuck in tyre. 8. Sway bar bushings have come loose or out. Metal on metal. 9. Check the control arms.