Thermoacoustics

Thermoacoustics is the interaction between the temperature, density, and pressure variations of a sound wave, and covers both engines and refrigeration systems built on that interaction. A thermoacoustic engine converts heat into sound energy, while a thermoacoustic refrigerator uses sound to produce a cooling effect; both rely on a stack, a porous solid structure that lets gas oscillate while staying in contact with solid walls, with heat exchangers on either side maintaining the needed temperature difference. The technology can run on low-temperature heat sources and needs no moving parts, which makes it attractive where reliability matters and mechanical simplicity is valued over a conventional engine design. At sound levels around 180 decibels, typical in thermoacoustic systems, the accompanying temperature swings reach about 24 kelvin, far above the roughly 40 microkelvin swing produced by ordinary speech. This description is adapted from Wikipedia contributors under CC BY-SA 4.0; changes were made. https://creativecommons.org/licenses/by-sa/4.0/