Make sure the AC isn't over-filled.
When the system shuts down the vapor turns back to a liquid
Worn serpentine belt and/or belt tensioner.
Make sure the radiator fan is working when the AC is on.
Loose or worn A/C drive belt. Tighten or replace. If serpentine belt, replace.
DC doesn't. AC might, since as the voltage varies the conductor experiences a cycle of heating and cooling that can make it vibrate, producing sound.
AC current is alternating between negative and positive at a rate of 60 hertz. That is the equivelent of 60 times per second. If you have flourescent or metal halide lighting, the ballasts on those lights contain magnets, and as the electricity alternates, it causes the wire to vibrate. Transformers will also make the noise.
If you mean that for producing the sound of speaking - air vibrations - there should be going chemical reactions and electrical impulses in the speaker's brain, electrical impulses should be sent to the muscles controlling his/her organs of speech - yes, in this recpect AC signals are inverted into the sound of speaking.
belts bad ac compressor timing chain.listen to see where the sound is comming from.that could help alot.
There are a whole slew of acoustic simulator pedals out there. You're best bet would be the Boss line of AC pedals. The AC-2 and AC-3 by Boss are pretty much as standard as you can get for acoustic stompboxes.
The ac compressor pump may be seized.
If the squeaking sound is heard only when the ac is on, the ac pulley may need a little bit of WD-40 sprayed on it.