Key difference, this one has demonstrated it working!
Jokes aside, I'm sure Clinkle had something working in a demo form but obviously the problem is sound as a digital communication medium is terrible outside of specific use cases (air gap attacks?).
re clinkle: i have definitely witnessed it working in person. not that that says anything in particular about clinkle. and yeah, knowing a lot of the people who worked there i definitely feel great delight and kinship with that particular blow up. and i worked at Color (Labs) for a bit, which, in terms of blow ups was like Clinkle before Clinkle, so i feel like i've had front row tickets to two of the best ones from that era! :)
Also Chirp. I wrote an error correcting modem for them. Getting a
simplex packet from A to B is the easy part. But any kind of
bidirectional protocol (say for flow control) falls apart in an
acoustic medium because duplex operations are thwarted by echo and
phase. It's a long time since I played with the idea but I reckon you
could do a lot more now with phones that have mic arrays and enough
CPU power to do more serious DSP.
as someone who worked at Clinkle (on backend) we did indeed have this early on. it was one of the demos used during my interviews to show me the app. The feature used infrasound instead of ultrasound like this article.
unfortunately coffee grinders and such would mess with transmission. the sound engineer working on it also left shortly before I started so the feature never got fixed and eventually killed.
