What does on top of the world mean? Feeling very happy, delighted, as in She was on top of the world after her roses won first prize. This idiom alludes to the peak of success or happiness.
An air wave is simply the sound or acoustic wave created by the source, which by definition is what travels through the air rather than the ground. It is what you hear. In most cases, the seismic velocity of the near surface materials his higher than the velocity of sound in air.