it is not an engine
and plz explain why it makes the noise
daniel , l am going to pick urs the best answer and u r my god. THANKS

The most correct answer would be the entire motorcycle makes noise. But l think u r asking about the exhaust system & specifically the muffler. This system gets the hot exhaust created by the combustion out of the engine & away from the bike. Many times people like to the sound of a ''louder'' exhaust so they replace it with a differently designed muffler. The sound is affected because of the way the exhaust exits the end of the muffler. That is how the low rumble is devoped that alot of bikers like. Is that what u were talking about?

the noise is made by the combustion of air and fuel in the cylinder

Above certain speeds on many bikes the main sources of noise are the air intake and the airbox, air is being collected and compressed into a vessel – it is a similar effect to the noise you make blowing across the neck of a bottle, but magnified.

the person riding it. Without the person the bike would not be started nor moved.

The wife on the back

the squid riding it that wo not quit beaking off