American Airlines' in-flight announcements include mysterious "grunting, moaning, and groaning"

Something weird is going on with American Airlines' in-flight announcement system. Multiple passengers say they've heard people making unusual moaning and grunting sounds, and the airline's explanation of what's going on seems to be bogus at best.

From Waxy:

View from the Wing's Gary Leff asked American Airlines about the issue, and their official response is that it's a mechanical issue:

American Airlines inspected the Boeing 737-800 as well as the P.A. system itself after these reports. They tell me that maintenance "determined the sounds were caused by an issue with the PA amplifier. There was no external access to the system."

This explanation feels woefully incomplete to me. How can an amplifier malfunction broadcast a human voice without external access? This isn't audio feedback, it's clearly the vocalizations of a human.

Professional reverse engineer/hardware hacker/security analyst Andrew Tierney (aka Cybergibbons) dug up the Airbus 321 documents in this thread, and is stumped too.

"And on the A321 documents we have, the passenger announcement system and interphone even have their own handsets. Can't see how IFE or WiFi would bridge," Tierney wrote. "Also struggling to see how anyone could pull a prank like this."