Why do airplanes have strange, double headphone jacks? (film, 6 minutes)
In his latest video, ThioJoe discusses the unusual headphones he received on a flight. Equipped with a strange plug that has two 3.5mm prongs instead of the standard single one, these headphones piqued his curiosity. As he admits, it was nowhere indicated that he should not take them, as they were placed on the seat along with other free items like pillows and slippers. He delves into why these headphones have such a unique plug. He claims these headphones are supposedly studio-grade with active noise cancellation but notes that the audio quality was not particularly impressive; what caught his attention was the plug itself. The airplane seat had a corresponding two-prong jack, and ThioJoe points out that one reason for the two-prong design may be to prevent passengers from wanting to walk off with them if they realize they have nothing compatible with this odd plug. He also mentions possible theories regarding them being a remnant from older pneumatic headphones found in vintage planes. ThioJoe believes it's likely a combination of these theories that explains the design choice. It might be assumed that each prong is meant for one audio channel, but upon closer analysis, he argues this isn't entirely accurate. In reality, each prong carries stereo audio with ground and microphone connections for active noise cancellation. ThioJoe explains how active noise cancellation works by having a microphone pick up external sounds, generating a cancelling waveform that is mixed with the audio. Interestingly, he points out that normally, the processing for noise-cancelling headphones occurs within the headphones themselves, while in this case, it happens via a system on the airplane. This set-up allows airlines to save money on headphone production, as it doesn't require chips or computing power within the headphones. This also reduces replacement costs and decreases the desirability to steal since they wouldn't function outside of the plane without that external processing. ThioJoe notes that even standard headphones could be plugged into the dual prong outlet, but the resulting audio quality was not worth the trouble. At the time of writing, the video has garnered 1,151,622 views and 38,589 likes, indicating its popularity and relevance among viewers.
Toggle timeline summary
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Introduction about strange headphones on a flight.
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Discussion on the unconventional two-prong plug.
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Wondering about the purpose of these headphones.
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Mention of studio premium status and questionable audio quality.
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Insight into the two-prong design to deter theft.
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Active noise cancellation feature discussed.
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Explaining prongs' function and channels.
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How active noise cancelling technology works.
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Description of external processing for noise cancellation.
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Benefits for airlines using this headphone design.
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Skepticism regarding the headphone's noise cancellation effectiveness.
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Options for using personal headphones with dual prong outlets.
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Unexpected audio outcome when using standard headphones.
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Conclusion and encouragement for viewer engagement.
Transcription
I was on a trip recently and on the flight they provided these headphones which had a very strange plug that has two 3.5 millimeter prongs instead of just the standard one. And I was reading afterwards that apparently I was not supposed to take these headphones, but how was I supposed to know? It was on the seat along with the other free stuff like the pillow and the slippers and literally nowhere did it say not to take them. Anyway, I was wondering what the purpose was behind this seemingly special plug and why these headphones have them and thought it'd make a good video topic. And actually there are a few reasons. A bit more relevant info about these headphones, first of all they say that they're supposedly studio premium headsets and claim to have active noise cancellation, but as you'll see in a minute it's not implemented in the usual way. Despite the premium name though, the audio quality was not actually anything special, I just cared about the plug. And in the plane seat there was a corresponding two-prong port it fits right into as you can see here. Some reasons for the two-prong plug that I was reading was because it would prevent people from wanting to walk off with them if they realize, well I don't have anything that's compatible with this weird plug, and then just leave them there. Although ironically that's exactly why I wanted to take them. I also read possible theories about it being some kind of redundancy or also a holdover from old pneumatic headphones in really old planes. And I think it's probably a combination of all of these actually. You might assume that each prong is for one channel of audio, so they're both mono, which is only partly true. Because notice that both prongs are actually stereo, where typically on each prong there's one channel being at the end, another channel at the middle, and then there's the ground. But it turns out that the four channels here are not actually for redundancy, but for the active noise cancellation functionality. Let me explain. As luck would have it, I actually found a github post where someone mapped out the wiring of these headphones and what each pin is for. So it turns out that the end tips of each of these two prongs are indeed for the right and left speakers, with the ground sleeve on one of the pins being the ground for both speakers, and the other middle and ground sleeves being for the right and left channel and ground for the two microphones. Wait, microphones? Yeah, that's actually how active noise cancelling works. There's a microphone basically next to the speakers, so when there's noise externally, it hears that and then creates a cancelling waveform, mixes that into the audio, and when all that goes into your ear, then it'll cancel out the noise part of it. But wait, you might ask, I have noise cancelling headphones and they don't require four wires. Well, that's actually one of the things that makes these headphones interesting. You see, normally the audio processing of active noise cancelling headphones occurs right on the headphones themselves. But with these, apparently, it occurs somewhere on the plane, on some external computer. I have a theory on the reason they do it like this, which I'll go over in a second, but basically what happens is the microphone picks up the noise signal, which gets sent to the plane computer through the wire and calculates the noise cancelling signal required. Then the computer takes the audio for whatever the person is watching on the in-flight entertainment system and mixes in that noise cancelling signal, which then gets sent out to the headphone speakers. Doing everything this way has some significant benefits for the airline. Mainly, it makes it way cheaper to produce the headphones themselves because none of the computing power or chips need to be on the headphones to do that noise cancellation. All the computing power exists on the plane computer side. Therefore, this means that they're also a lot cheaper to replace if a pair of brakes or someone walks off with them. Also, theoretically, it makes them even less desirable to take for yourself because off the plane, they don't even have the active noise cancellation feature. It wouldn't work without that plane computer, even if you had some kind of adapter to use it with your own devices. So you'd just be left with some mediocre regular headphones. In fact, the noise cancellation didn't really even work all that well in the first place. I can't imagine they use top of the line microphones. I will point out that there are actually adapters that you can buy specifically made to let you use your own headphones with the dual prong outlets, or there are some generic stereo to mono splitters that should work too, I imagine. So if you are on a plane with this port, you still can use your own headphones and the active noise cancellation would work because yours would be doing the cancellation on the headphones themselves. There's also splitters and adapters that do the reverse, which would combine the mono channels. But again, these headphones are not really worth bothering that with. The one other strange thing I noticed is that when I plugged my actual regular headphones with the stereo 3.5 millimeter jack into one of the dual prong plugs, audio did actually come out of both speakers of my headphones. So I don't know if there's additional processing going on that might detect if there's only one thing plugged in. I have no idea. I thought I'd just point that out. There might be more going on even still. So if you ever wondered what the purpose was behind this, or maybe you didn't know it existed in the first place, well, now you know. If you did find this video interesting, definitely give it a big giant thumbs up for the YouTube algorithm. It definitely helps. And if you want to keep watching, the next video I'd recommend is where I talk about how you might be using the wrong USB power cable, that you're not getting the full charging speed of your device on. You can just click that right there. And thanks so much for watching. I'll see you in the next one.