There used to be a thick glass panel in front of it, but no more.
Open your new MacBook Air, place a single grain of sand smack in the middle of the keyboard between the G and the H. Close the lid.
Turn around and sit on it.
Tell me all about glass then. If you record it I'll have a listen.
Alternatively, throw a pinch of sand on the keyboard, close the lid, bag the Mac. Now, with some vigor, take it out blindly by any corner and trow it down on the thick wooden table, slamming it with it's own weight.
A few times.
And tell me how that gentle test went for you. :)
There used to be a thick glass panel in front of it, but no more.