What causes for an interference sound to occur in smartphones?


Sample of an interference sound: https://youtu.be/uPYyrS7fc7g

In: 1

This is caused by the method used for sharing the transmission channel: time-division multiple access. It is used in second generation digital telephones like GSM.

There are multiple telephones on a channel and they take turns sending and waiting or receiving. While the phone is transmitting during its time slot, it induces a voltage in nearby wires. When it is idle, this doesn’t happen. The result is a square wave pattern. The device can’t respond quickly enough to the data being sent. If this energy hits an audio amplifier, the electrical signal is boosted and sent to a speaker.