Why are you able to hear the sound outside your plane

Why is sound rendered outside your plane once your cockpit is closed?

Because glass doesnt fully stop sound. It will dampen it though.

Even with all of my windows closed, I can still hear cars drive by my house.

I don’t mind hearing sounds like other planes, but it’s really stupid you can fly a jet with mach 1 over a battlefield and locate a tank because of the idle engine sound.


Try it with your house travelling at 400 mph thru the air.
Oh and, with an un-muffled generator sitting in your lap.
And and, while you are wearing headphones so you don’t go deaf from the above two.