The answer is: Sound waves and some earthquake waves have compressions and rarefactions.
Rarefaction is the reduction of an item's density, the opposite of compression.
There are three types of mechanical waves: transverse waves, longitudinal waves (sound) and surface waves.
Sound is transmitted as longitudinal waves, also called compression waves.
Seismic waves are fundamentally of two types, compressional, longitudinal waves or transverse waves.
