Guitar processor noise...? BZZZZZZ!

Back in the late 90s to early 2000s when cell phones were just coming into their prime.

A friend could tell you he was about to get a call.

Her PC speaker would pop and click a few times then the phone would wake up and start to ring.

My assumption was that the phone was sitting in a low power state untill a tower pinged it, then it would go to higher power state and reply. The noise I'm guessing was the cell phone signaling the tower.

We proved it out (that the cell was the interferiance) with numerous blind tests.