funny enough the highest reachable frequency theoretical is into the light spectrum, audible however is proven to be from about 5 to above 48kHz for so far you still can speak of audible.
on the low end of the range its the resonance of your body, which can make you very sick, like seasickness what you "hear", above approx. 15kHz the sound is no longer detected by the ears, but still noticeable.
Plasma indeed covers the entire range.