Chili, you got me there. I meant oscillating between "Whole Pressure High" and "Whole Pressure Low". Of course, the only way I can think of creating this is to expand and contract the whole volume at once.
Yeah, but that still won't make your mix any louder!
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The thing with your thought experiment, Brent, is that the volume change cannot be instantaneous. There has to be movement of the walls in and out, even if it takes an inperceptenbly small amount of time, because we're talking about a change from one location or state to another. The very idea of "change" requires time; it "was" like that, "now" it's like this.
If the walls just quantum jumped without movement, there'd be no change in air pressure because the walls would jump right across the air volume instead of pushing in the air molecules with them.
That movement means each wall is acting like a speaker membrane causing pressure changes in the inside volume. But that pressure change takes time to propagate, it does not happen uniformly across the entire room volume at the same time. Instead, near the wall the pressure will build up first, and it will then take the form of a pressure wave with will travel inward across the room. At such a point it's in basic principle no different than a similar pressure wave that came from somewhere inside the volume and simply reflected off the wall.
Extrapolate that to 6 surfaces, and the interactions get a bit more complicated, but the basic idea stays the same; you will have pressure waves moving through the volume and not instantaneous pressure change across the whole volume.
The atmosphere is like a liquid, changes in it can only propagate through it like waves, not occur simultaneously across the whole volume.
G.
and I'm not sure I'm completely following.
