What is rarefration?

Answer 1

Rarefaction is the decrease in the density of something which is also the opposite of compression. As far as I know rarefration is not a word but i think you are meaning rarefaction.

Answer 2

"Rarefaction" refers to the reduction in density of a medium, such as air, which occurs when sound waves pass through it. This phenomenon causes the particles in the medium to spread out, resulting in a decrease in pressure and density compared to the surrounding areas.