The sound is said to be 'absorbed' or 'lost' when it is converted to heat inside a material. For this reason, materials that are soft and porous, like cloth, are good at converting sound to heat. Materials can be made absorbent by embedding an array of little irregularities directly into the material, such as air bubbles. The ordered movement of atoms is also made more disorderly when sound travels through acoustically absorbent materials. When some of the sound wave is converted to heat, the motion of the air molecules becomes more disordered and the amount of heat increases. In other words, air through which sound is traveling already contains some amount of heat. Note that the air molecules already have a motion that is somewhat disordered. Therefore, when a sound wave hits a rough surface, the motion of the air molecules gets scrambled up a bit.

As another example, the rough surface of an object constitutes a collection of irregularities that the sound wave encounters. The dust particles mess up some of the ordered motion, and therefore convert some of the sound to heat. This effect happens a lot whenever the sound wave encounters irregularities as it travels.įor instance, dust particles in air are irregularities that randomly interfere with the vibrating motion of some of the air molecules that make up the sound wave. This effect always happens to some extent. Therefore, all you have to do in order to turn sound into heat is transform some of the ordered movement of the atoms and molecules into disordered movement. Heat is the disordered, random, movement of atoms and molecules.

Sound is the ordered movement of atoms and molecules in rapid waving patterns. Sound and heat are both macroscopic descriptions of the movement of atoms and molecules.

In fact, sound waves almost always generate a little bit of heat as they travel and almost always end up as heat when they are absorbed. Public Domain Image, source: Christopher S.

Soundwaves definition