system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is it about cellphones that causes speakers to do that morse code thing?
gpt
The sound is sent to the speakers over wires as an electrical current with varying strength.

Almost all wires behaves as antennas to some degree and can send and receive radio signals, often unintentionally.

So what happens is that the radio signals from the phone antenna are picked up by the wires, and this changes the current that reaches the speaker (it can get stronger or weaker than it's supposed to be).

This leads to the noise you hear.