Engine Running Loud

First check that the engine has oil and coolant. It is quite possible that the exhaust is has a leak. Is the leak worse when the car is started from cold. There are heat shields covering the exhaust manifold that would need to be removed to inspect the manifold itself for cracks, the exhaust manifold has a gasket between it and the catalytic converter, the gasket or the studs and hardware there may be missing or blown out. The exhaust pipe it's self or flanged joints may have cracks or bad gaskets or the exhaust box/muffler may have holes in it. Leaking exhaust may leave a black mark (carbon) at the source of the leak, missing hardware or holes in the exhaust system should be more obvious.