[ST]

On Saturday, January 25, 2014 10:15:56 PM UTC+8, news wrote:
As for air density changing every few centimeters in a calm room, I don'=
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think so. Air and any gas evenly disperses itself in its give area; in t=
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case a room. The atmospheric pressure is the force exerted on the walls =
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everything else in the room by the air molecules bumping against everythi=
ng.
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Shaun

But they don't stand still. They move around. Air is a poor conductor of so=
und. Just like a ripple which can be seen clearly in calm pond. The air sme=
ars the ripples by its movement. Your measurement at source of the sound an=
d at the receiving end of the ears is not going to be the same at longer di=
stance.