Same thing different name. I said ultrasonic because that's the wavelength you need for it to be compact The basic way of working it is basically * lowering t

Same thing different name. I said ultrasonic because that's the wavelength you need for it to be compact The basic way of working it is basically * lowering the pressure of gas causes it to cool, increasing it causes it to heat * creating standing wave in a gas in pipe means the low pressure part will be cold, high pressure part will be hot, and the difference will equal to basically pressure induced thermal difference sooo a fancy speaker in the tube. Already stuff that can be bought, just didn't get to the level required for consumer stuff. Supposedly they can be pretty efficient too. Would also be basically noiseless, as the ultrasonics are limited to the cooling tube and easier to dampen anyway.