Fluorescent lamps (don't) have ears

10 5 Share I never mentioned it publicly, but early in my career, I did a part-time stint in technical surveillance countermeasures (TSCM) — a fancy term for sweeping office environments in search of listening devices and other unauthorized spy gear. In practice, the job entailed getting several certifications, hauling around a bunch of costly suitcases, and above all, spending some time with ex-spooks, listening to stories that would make James Bond blush.

The discipline is rather hush-hush, so you never know what’s real. One of the more striking claims I remember from the training was that fluorescent lamps could be used to passively eavesdrop on conversations in the room. This makes some sense: the tubes are filled with glowing gas. A sound wave propagating through this medium could theoretically produce subtle luminosity fluctuations that could be picked from afar.