Are fans a problem because the are physically audible or do they introduce problems in the signal chain? In my room my AC and electric fan are way louder than any pc fan.
It was said that if you pass a magnet to a coil, you induce current and if you pass current on the same coil, you also induce magnetism.
In reality, depending on the position of the fan's coils, it either requires current or induces current through inertia. Since the fan is powered from the same power supply, this continuous current draw/discharge cycle will re-introduce noise to the system causing havoc to other electronics.
Your AC and electric fan are not powered from the same psu, but the pc fans are.