They say that "The camera is not disconnected in hardware because its field of view is completely obstructed with the lid closed."
I read some time ago that the LED used to be hardware controlled, but switched to being software controlled at some point.
Kind of like this: http://news.mit.edu/2014/algorithm-recovers-speech-from-vibr...
In some of their experiments, the researchers used a high-speed camera that captured 2,000 to 6,000 frames per second..
I haven't checked, but I would be surprised if Apple uses cameras that are capable of that as normal user-facing webcams in their laptops ...
Recovering meaningful audio signal (which usually has lots of data above 1 kHz) from the <100 Hz sampling done by a camera seems difficult, Nyquist and all, right?
In other experiments, however, they used an ordinary digital camera. Because of a quirk in the design of most cameras’ sensors, the researchers were able to infer information about high-frequency vibrations even from video recorded at a standard 60 frames per second.