Yes they do like the sound...they also like the moisture sweating on the suction line. A lot of a/c's are filled with leaves and debris, dead bugs too for them to eat. Refrigerant lines also make a nice entry route into the house so they can eat people food.
Termidor SC works well on them, Chlordane is not legal, and hasn't been since 1987. As much as I try I cannot kill them all, but glad the ants are helping your business out.