Rarefaction

Imagine you have a big bowl of marbles. If you spread them out, there will be more space between the marbles, so they won't be as close together. This makes them less dense. That's like the rarefaction in sound waves.

Sound is made up of waves, and those waves push air molecules around. When the waves are closer together, the air molecules are more packed together, so the sound is louder. But when the waves are spread out, the air molecules are more spaced out, so the sound is quieter. This is called rarefaction.

So, just like the marbles in the bowl, when sound waves spread out and there's more space between them, the sound is less dense and quieter.