I was thinking about Loren's concept of a virtual array-microphone on my  walk this morning. I was breaking it down into simplest cases and came  up with an interesting software idea.

The simplest case is locating a tone-generator on a straight line between  two mikes, right? The difference between the sine waves is directly  proportional to the relative distance of the mikes to the tone generator:

Add in volume, which is (inversely) proportional to the square of the distance of  the signal from the mike, and it should be pretty easy to get a fix on a  single tone generator. (Oh, excellent, we can make a sniper detector!)

Things get quite harder when you start thinking about "real" noise signals, and get really hard when you think about overlapping signals. (As a matter of fact, on my walk, I came to suspect that 16-bit volume might be the Achilles heel of the virtual mike array). But leave that aside for now…

My new idea was "well, what if the laptops were themselves the tone generators?" Could that be used to locate laptops in physical space?

And then (as my walk ended), I thought "…And then the laptops use Morse code to send their IP addresses and initiate meeting software."

Things get a little tougher with multiple laptops in X,Y but it's easy enough to figure out protocols to get around that. Essentially, you'd sit down at a meeting, hit "go", and it would sound like acoustic modem coupling. Either that, or it would have cool WWII submarine sounds, and the software would be called "The Search for Red Toshiba." Anyway, after a few seconds, "participating laptops" would appear on a virtual table and you could match participant names to faces; shared note-taking / agenda things would start to synchronize; etc.

So basically, is a SONAR-based discovery protocol possible? Valuable? Any other ideas on "meeting room" applications?