Sound waves are mechanical waves because they need a material medium for propagation, like air or liquids like water or metals like silver.
The defining criterion for a mechanical wave is that it needs a material medium like air, water and metals for its propagation. Sound waves need a medium for their propagation. When sound waves travel through the air, they propagate in pressure variations wherein the high-pressure regions called compressions and low-pressure regions are called rarefaction.
- A sound is a vibration that propagates through a medium in the form of a mechanical wave.
- The medium in which it propagates can either be a solid, a liquid or a gas.
- Sound travels fastest in solids, relatively slower in liquids and slowest in gases.
- The number of rarefactions and compressions that occur per unit of time is known as the frequency of a sound wave.
- The speed of sound is highest in solids because the atoms in the solid are highly compressed.