What is rare faction of sound wave?

Answer 1

A rare faction is an area of a sound wave where there is lesser compression of the medium,ie Rarefaction is the reduction of a medium's density, or the opposite of compression

Answer 2

A rarefaction is a region in a sound wave where the particles are spread out, resulting in lower pressure than the surrounding areas. This is in contrast to a compression, where particles are closer together and pressure is higher. Rarefactions and compressions alternate in a sound wave as it travels through a medium.