I wonder if a plasma loudspeaker could use a mechanism similar to a stun gun. The spark from a stun gun does not produce any perceptible heat in close proximity because -- despite being a 100,000 volts -- the power is not enough to raise temperature sufficiently to burn the skin.
That being said, the stun gun does make sound when it sparks. I assume that an equipment similar to the stun gun could be engineered so that it could produce sparks that would cause the intended sound [e.g. speech or music].
Conventional plasma speakers produce sparks that reach as high as 2,000 Celsius.
If an high-voltage, low-amperage electric current of 1,000 Hz frequency is passed through air, a 1,000 Hz tone will result.