Gannon...How do you know that? Did you make some measurements? I have observed (while traveling in the Suez canal) that the bow wave of a ship is a trough before the crest. Likewise a Tsunami is preceded by the ocean going out before the wave comes in. In the case of sound in air...consider a drum. Surely the polarity of the sound wave will differ depending on which side of the drum you hear it from.
The behavior of a sound wave propogating in air is a whole lot more complex than you think. And anyway, as others have noted the polarity of signal on recordings is so mixed up that, IMHO, it is a waste of time to worry about it.
