Thermoacoustic engines (sometimes called "TA engines") are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another (this requires work, which is provided by the loudspeaker) or use a heat difference to produce work in the form of sound waves (these waves can then be converted into electrical current the same way as a microphone does). These devices can be designed to use either a standing wave or a travelling wave. Compared to vapor refrigerators, thermoacoustic refrigerators have no coolant and few moving parts (only the loudspeaker), therefore require no dynamic sealing or lubrication. History The ability of heat to produce sound was noted by glassblowers centuries ago. In the 1850s experiments showed that a temperature differential drove the phenomenon, and that acoustic volume and intensity vary with tube length and bulb size. Rijke demonstrated that adding a heated wire screen a quarter of the way up the tube greatly magnified the sound, supplying energy to the air in the tube at its point of greatest pressure. Further experiments showed that cooling the air at its points of minimal pressure produced a similar amplifying effect. A Rijke tube converts heat into acoustic energy, using natural convection. In about 1887, Lord Rayleigh discussed the possibility of pumping heat with sound. In 1969, Rott reopened the topic. Using the Navier-Stokes equations for fluids, he derived equations specific for thermoacoustics. Linear thermoacoustic models were developed to form a basic quantitative understanding, and numeric models for computation. Swift continued with these equations, deriving expressions for the acoustic power in thermoacoustic devices. In 1992 a similar thermoacoustic refrigeration device was used on Space Shuttle Discovery. Orest Symko at University of Utah began a research project in 2005 called Thermal Acoustic Piezo Energy Conversion (TAPEC). Niche applications such as small to medium scale cryogenic applications. Score Ltd. was awarded £2M in March 2007 to research a cooking stove that also delivers electricity and cooling for use in developing countries. A radioisotope-heated thermoacoustic system was proposed and prototyped for deep space exploration missions by Airbus. The system has slight theoretical advantages over other generator systems like existing thermocouple based systems, or a proposed Stirling engine used in ASRG prototype. SoundEnergy developed the THEAC system that turns heat, typically waste heat or solar heat into cooling with no other power source. The device uses argon gas. The device amplifies sound created by the