The interference is coming from your mobile devices. Even when you’re not using your phone it’s generating electrical signals that can cause interference. You can hear this by placing your handset close to your microphone. The microphone’s capsule and circuitry may act as a mini receiver and the interference from the phone will become audible on your computer’s speakers or on your headphones. It’ll sound like a buzzing or a kind of very rapid morse code. To avoid this interference, keep your phone away from the mic and the cable.