Why does touching the microphone cable stop my headphone from humming? This might sound like a techical problem, but i'm more interested in the physics aspect of it.
I have headphones that are connected to my pc with a single cable.
I also have a microphone attached to the headset, that is connected to the pc with another cable.
Both cables run roughly along the same path and are plugged into the pc with maybe 0.5" between the jacks.
Heres the problem/phenomenon:
I have a constant humming in my headphones (only on the right speaker) that changes in pitch when my pc is under load.
That started happening about half a year ago.
When i take the microphone(!) cable into my closed fist, so that it is completly sorrounded my my palm and fingers, the humming sounds disappears completly. Tried it at several segments of the cable.
I've tried wrapping a few layers of aluminium foil around the cable, but that does not achieve anything, atleast nothing that i can perceive.
Does anyone have an explanation on why this is happening/what the physics behind it are?
My guess would be something about capacitance, but i dont really know much about it, so im not really sure.
Any Ideas are appreciated.
 A: Humming in an audio circuit is evidence in general of a grounding problem somewhere in the circuit, which allows things like radiated or conducted electromagnetic noise to bleed into the audio signal from other parts of the device or from other appliances in its vicinity.
By grasping the wire in your hand, you are coupling the signal in the wire to a (somewhat weak!) ground (your body) and also coupling the mic signal path to the headphone signal path. If there's a capacitor inside the PC which is supposed to be doing this, but that cap has croaked, then you get the hum in your headphones.
The fact that the hum changes pitch when the PC is under load demonstrates that the source of the hum is probably the power supply inside the PC. The fact that the problem started suddenly indicates that something has failed inside the PC. The fact that it is specific to one channel of the audio output circuit points to a component that is connected to the power supply and the driver amp for that channel- probably a small-valued electrolytic capacitor, because faulty electrolytic caps are a known plague on the electronics industry.
The other possibility is a bad or weak ground line in the headphone shield or the microphone shield wire(s). The ground wire connections inside these mini plugs are notoriously flimsy, so try a new mic/headphone assembly and see if the problem disappears.
