Ah yes, unshielded speakers and cellphones. The terrible noise in the early 2000s letting me know my parents were calling the cellphone they gave me for college in order to force me to keep in touch.

The scenario that you describe is one of those cases where the party you empathise with most changes as you grow older.

I've never understood why this happens. Is it my phone sort of ACKing the call back to the tower? Because it has to be my phone sending something back, right? Random cell signals are hitting the speakers all the time.