Error being blown out of your mouth is similar to DC ( direct current ) and that it’s a continuous wave of air with frequency zero. While speaking is like AC ( alternating current), a longitudinal wave that moves back and forth at a variety of frequencies.
Slowly varying signals like the waveforms generated by speech in all its forms are still AC signals and need to be treated as such for engineering purposes.
So to bring it back to electric circuits, a range of, say, 0V to +3V would be considered AC?