Mystery radio station playing through headphones. How to find all sources of sound?

I'm going to go with Interference. Very hard to know exactly what causes it, but could be fixed by experiment with things like: Re-route wires, unplug unused things, clean plugs, different outlets, sit in a different position, move things around...

• Tom's Guide - Picking up radio station signal through my speakers
• audio-technica Resolving Interference Problems

Every low-frequency Amplifier picks up the strongest audio signal from local broadcasting stations. When you connect the headphones their cord works as an antenna additionally amplifying the signal. This is caused by poor shielding of headphone's cable.