Plasma speakers (sometimes called flame speakers if the source of the plasma is combustion rather than gas ionization) are a form of loudspeaker which vary the intensity of a plasma, rather than using a magnetic field to push or pull a conventional driver, to create compression waves in air (which a listener perceives as sound).
A plasma arc loudspeaker or plasma-dynamic loudspeaker is a loudspeaker that creates sound by varying air pressure through a corona discharge or electric arc. It is an evolution of William Duddell‘s “singing arc” of 1900 and, in recent times, modern research into spacecraft propulsion in the form of the ion thruster.
Plasma tweeters are claimed to be an improvement on traditional tweeter designs because the driver has very little mass, and so low inertia, reducing distortion and increasing transient response. Because of their inability to move large volumes of air, they are limited to reproducing only very high frequencies, and are therefore usable only as tweeters. Most of those who have heard them claim they are notably sharp and clear.
Science does rule.
Learned about this from Wired.