If Technician A hears noise from inside the muffler while inspecting an exhaust system, what is likely happening?

When noise is heard from inside the muffler during an inspection, it typically indicates that the internal components of the muffler are deteriorating. This can occur due to a variety of reasons, including corrosion, as exhaust gases and moisture can create an environment that promotes rust and decay from the inside where the sound baffles and internal structures are located.

A muffler that is rotting out from the inside may develop internal perforations, leading to the rattling or metallic noise that is often noticeable when the vehicle is running. This deterioration impacts not only sound quality but also exhaust flow efficiency, potentially leading to more significant performance issues.

While the option referring to the muffler rotting from the outside is plausible, it does not typically create internal noise. Similarly, while deterioration of the catalytic converter can produce similar sounds, particularly if its internal components are breaking down, the specific context of the question centers solely on the muffler. Therefore, the scenario described aligns closely with the muffler experiencing internal decay leading to noise, making it the most appropriate answer.