An experimental thermoacoustic natural-gas liquefier has been built and tested. It comprises a standing-wave thermoacoustic engine and a traveling-wave refrigerator (a pulse-tube refrigerator). The engine and refrigerator share a common resonator, filled with 3 MPa helium gas and operating at 40 Hz. The engine is heated by external combustion of natural gas, while the refrigerator cools and liquefies a methane stream, so the complete system functions as a natural-gas-fired natural-gas liquefier having no moving parts. Both the engine and refrigerator have operated above 20% of their respective Carnot efficiencies. Compared to other thermoacoustics research hardware, this experimental system is very powerful, with up to 20 kW of acoustic power delivered from the engine to the resonator and up to 2 kW of refrigeration power at 130 K provided by the refrigerator. Nevertheless, much larger systems will be required for commercial success. [Work supported by the Office of Fossil Energy in the U.S. DOE and by Cryenco, Inc.]