In the earth's atmosphere , the column of air is also the amount of air that extends vertically in the direction of space from any point on the earth's surface . It exerts a hydrostatic pressure , the air pressure , on all objects in it (also called "disturbances") or on the ground. The change in pressure with altitude above the ground is approximately described by the barometric altitude formula ; the atmospheric temperature gradient , d. H. the change in temperature with height above the ground is described by the dry adiabatic or wet adiabatic temperature gradient .
With wind instruments , the column of air inside the body is the actual sound generator. It is made to vibrate by the instrument mouthpiece , and the pitch produced depends on its length, thickness and air pressure .