alt Hacker NewsI as skeptical as the next guy when it comes to the claim that ambient audio modulates the fluorescent light. But I could sure use more details on what analysis was done to the photos. Sounds like there were several photos taken, say 100ms(?) apart. Then the photos were subtracted pixel-by-pixel to look at the variations in time (between photos) or spatially (neighboring pixels)? I still think a photo-diode AC-coupled to a high gain amplifier fed into an oscilloscope would be the more conclusive test. Do a audio frequency sweep from 100-10kHz. Both with the fluorescent light on, and then again with the light off (as a control, in case something else in the setup is sensitive to the audio).
He has the integration time set to 1/8000 s.
I assume the idea is that you're effectively randomly sampling (with each shutter press) that amount of time of the sine wave. You should see a distribution of brightness if there's a signal present, unless you get unlucky and sample at the same brightness (many would be required). Capture many with and without audio signal present, compare std deviation. If they're the same, no signal.
But yes, truly terrible lab report. ;) Who knows if this data is meaningful.
I wonder if the original rumor came from a bulb with a failing ballast, with a "less stable" arc, or maybe with a mic/diaphragm integrated into it, that modulated the light by sinking some current? I always assume these more wizardly things are based in truth.