Air particles do not travel in any motion. They oscillate around a point in space. The rate of this oscillation is known as the frequency of the sound wave and is denoted in cycles per second (cps) or hertz (Hz). The amount of compression/rarefaction of the air is the amplitude of the it.

Sound  is a vibration that generates an acoustic wave. The distance between consecutive peaks of compression or rarefaction is the wavelength of the sound wave (denoted by λ). Fast traveling wave results on a greater λ