[wccrawford]

While I think it -could- work, no 2 people could authenticate at the same time, even to different access points. That would be a nightmare for conventions.

[brlewis]

I wouldn't read the word "silence" in this article as a precise term. Check out their abstract/paper:

http://www.usenix.org/events/sec11/tech/tech.html#Gollakota

The abstract says they've made it work on busy networks.