Acoustic data/voice connections are solved COTS hardware bits - https://www.l3harris.com/all-capabilities/acoustic-general-p...

I've been thinking about this problem.

Would an iPod glued to the inside that played yellow Submarine by the Beatles.

At what range would that be detectable? How long could it last?

Edit: even better this banger on loop https://youtu.be/uzR5jM9UeJA