The question is not "can you transmit digital information over audio". That's an obvious yes. The question is, can laptop speakers transmit at ultrasonic frequencies, and can a laptop microphone pick those frequencies up sufficiently to actually communicate.
This guy used 17 and 18 kHz as carriers. That is within the hearing range of young people, but a quick experiment shows that either my desktop speakers cannot reproduce 17 kHz, or I have recently become too old to hear 17 kHz.
> This guy used 17 and 18 kHz as carriers. That is within the hearing range of young people, but a quick experiment shows that either my desktop speakers cannot reproduce 17 kHz, or I have recently become too old to hear 17 kHz.
Maybe, but you can test your hearing range more easily by putting on a set of headphones and experimenting with the linked signal generator -- reasonable quality audio headphones should easily be able to exceed your own hearing range on the high end.
And chances are typical computer speakers should also be able to exceed a normal hearing range.
>or I have recently become too old to hear 17 kHz.
If you're in your mid-20s (and you're on HN, so you probably are), it's not terribly unlikely that you've recently lost that part of your range. In my experience (back when I was young enough to hear those frequencies), even crappy speakers can usually go up to 20kHz easily. Very low frequencies are another story.
> The question is, can laptop speakers transmit at ultrasonic frequencies, and can a laptop microphone pick those frequencies up sufficiently to actually communicate.
Given two separate examples of running code, the question is really what percentage of laptops can do this. It's possible that some systems have filters but so far I haven't found one.
This guy used 17 and 18 kHz as carriers. That is within the hearing range of young people, but a quick experiment shows that either my desktop speakers cannot reproduce 17 kHz, or I have recently become too old to hear 17 kHz.