The Structural Resonance Theory proposes that standing wave that creates the airborne sound wave is simpler than the airborne wave that is created. This interface exists, in these examples, on the surface of a timpani or across the F-hole of a Double Bass.
We tested many different instruments a various other sounds and the results were always the same
Thomas Wagner Vibrometer tests
One thing that has always puzzled me is how can a compression wave form in an uncompressionable medium. Current physics treats this wave as a compression wave. If this is true then it follows that the nature of the wave is different than the compression wave that forms in the air. I propose that a sommilar tyoe of wave occurs in the air along with the common compression wave. We do not notice it because the density of the air is so much les than in a solid or liquid.
A couple of years ago a very powerful thunderstorm occurred and as I listened a bolt of lightning struck in an open area next to where I was sitting. I estimated the bolt hit about six or seven hundred feet away. It was followed by a very loud thunder clap that shook the house but before this clap I actually heard the flash. It was not terribly loud but was a discernible sound. It was rather short.
I mentioned this to Chris Rogers at Tufts University. Chris did the vibrating string photographs that are on Vibrating Strings page. He suggested I see if it happens again. Several months later the very same happened again and again I heard the flash. This establishes my second airborne wave. This could be worth working on as the secondary wave would have the information of the sound before it was corrupted by the viscosity of the air. We attempted an experiment with the laser vibrometer but the results were inconclusive.