I used to love trying to surreptitiously unplug my traveling companions’ headphones so I could blow into the end of the tube. Never once pulled it off.
I remember being able to select the pilot coms. I was nervous on my first flight as a kid, and it was very calming to hear the preflight checklist and ATC communication in the classic pilot cadence. This was pre 9-11.
I did wonder on my last flight if I could use SDR & android to listen in.
Some airlines might still have the "listen to ATC" feature available, but in my experience, it's the pilots' decision whether that's available or not, and I've only ever been able to use it on a United flight once.
Sirius XM on JetBlue also has an "ATC channel", but I've only ever heard silence there, and I'm not sure if that's a similar thing (i.e. sourced locally), or just a random ATC feed from somewhere in the country relayed via satellite.
EDIT i'm wrong the speaker was inside the armrest.
I wouldn't be surprised if the channel selector wheel was a simple mechanical acoustic coupler rotating to connect or cap upstream source tubes. I remember it as well flying in the late 80s or early 90s.
I get what you're saying, and I think that's plausible. But as far as I'm concerned, an acoustic coupler is/was a type of modem, into which you plugged an ordinary telephone handset. You had to have a telephone that had hemispherical mike and earphone; it didn't work with e.g. a trimphone. Expected performance: 9,600 bits-per-second.
> The sound is transported along the tube via air — a very simple solution. Though this also explains why they sound absolutely terrible.
I see it is simple, but I wonder, would it be possible to use different sound medium ("conductor")? Some liquid, water perhaps? Would elasticity of the tube eat more signal than is lost in the air? Too heavy? Leaky? Questions…