Loud Mouths Are Relative

We're sitting in the drive through at Caribou, and a freight train comes up on the tracks behind us and blows the warning blast on its horn (whistle?).  I had my window rolled down, and it was LOUD.  The boys were suitably in awe.  Then this conversation takes place:

N:  "Whoooooaaaa.  That was a super long train!"
Me:  "It sure was!"

N:  "And Ab, it was REEEAAAALLLY LOUD!"
Me  "Yes.  Did it hurt your ears?"
N:  "It was even louder than my mouth!!"

I know that he really meant that it was louder than he could make the train sound with his mouth, but (I love this kid, so this is not an insult, only an observation) he has a VERY loud mouth in every way possible, which makes his statement SO funny.