Answer:
rarefaction is the correct answer.
Explanation:
Rarefaction is defined as the reduction in the density item.
Rarefaction takes place mostly when the particles present in the gas become extra scattered out.
Sound need to a medium to travel and the air is the most common medium. As the vibrating object move in the forward direction, the air gets compressed and creates a region of high pressure and the high-pressure area is called compression. This compression begins to move apart from the vibrating object.When the vibrating object moves in the backward direction, it creates less dense areas called rarefaction.
Thus The less dense areas in a sound wave are called rarefaction.
