You couldn't hear a dump truck driving through a nitroglycerin plant.
6 seconds sound clip from the Christmas Vacation (1989) movie soundboard.
You can hear this line at 01:19:29 in the Blu-ray version of the movie.
Quote context
[...]
- Do you hear it? It's a funny squeaky sound.
- You couldn't hear a dump truck driving through a nitroglycerin plant.
- We can't let it get out of the living room.
[...]