Sound and air stream

Sound in its most usual sense means an air pressure disturbance that can be heard by the human ear. Air molecules close to the source of the sound vibrate locally and their kinetic energy spreads as a wave away from the source of the sound. The transmitting material itself does not move from one place to another. A characteristic of sound is that it propagates in every direction (a spherical wave) with a constant velocity (about 340 m/s in normal temperatures and air pressure). The sound’s volume is dependant on the amplitude of the wave-motion.
 
An air stream will arise when air moves from an area of high pressure to an area of low pressure. Then air is moving from one place to another. The air stream has a certain direction and velocity that can vary at different points.

Transmission of sound and air stream