What is the term for the area of a sound wave where air molecules are spread out?

The area of a sound wave where air molecules are spread out is referred to as rarefaction. In a longitudinal wave, such as a sound wave, molecules of the medium (in this case, air) vibrate in the same direction as the wave travels. As the wave moves, some regions experience compression where molecules are bunched together, and other regions experience rarefaction where molecules are more spread out. Rarefaction specifically corresponds to the areas where the density of air molecules is lower compared to the surrounding regions, allowing us to visualize how sound energy travels through the medium. This concept is crucial for understanding how sound waves propagate and is fundamental to the study of wave physics.