Thermoacoustic prime movers have been developed for operation in the low ultrasonic frequency range by scaling down the device size. The developed engines operate at frequencies up to 23 kHz. They are self-sustained oscillators whose dimensions scale inversely with operating frequency. The smallest one being 3.4 mm long with a 1 mm diameter bore, i.e. the engine inner volume of 2.67 mm3. The generated sound levels reached intensities in the range of 143–150 dB in the low ultrasonic range. The miniaturization of thermoacoustic engines will lead to the development of device arrays.