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One thing that's not obvious to me from TFA is why an incandescent bulb is called out specifically. It seems to me that a hanging LED bulb would be just as vuln

One thing that's not obvious to me from TFA is why an incandescent bulb is called out specifically. It seems to me that a hanging LED bulb would be just as vulnerable, as might a glass chandelier of sorts. I also wonder whether Christmas trees with hanging ornaments are vulnerable. These are often placed in a prominent window, so it might be quite easy to start listening in on conversations in people's living rooms or business lobbies.

buran77 6y ago
Maybe the filament is more susceptible to vibration and "flickering". But it may just be my interpretation, the text doesn't really spell it out as such.
- braythwayt 6y ago
  A couple of other comments mentioned the filaments, but the article says nothing about clear bulbs. They are very much in fashion these days, but most incandescent bulbs are frosted, so it seems to me that if you want to use a laser on the filament, there would need to be some considerations around photons passing through the frosting and reflecting off the filament.
  - buran77 6y ago
    The bulb doesn't have to be clear, the filament vibration would make the light flicker visibly (for sensitive equipment that is) even if the glass isn't clear. So it may be that the filament is far more susceptible to vibration than the glass on any type of light bulb. As I said, this is my interpretation, the text doesn't make it clear to me.
  - steverb 6y ago
    I don't think it's about observing the filament directly, just that the filament basically being a spring is more susceptible to vibrations which would change the amount of light emitted. I am totally guessing at that, but it seems reasonable.
- LgWoodenBadger 6y ago
  The filament is in a vacuum...
  - close04 6y ago
    Almost no incandescent light bulb has a vacuum inside. They are filled with low pressure inert gas (mostly argon sometimes mixed with nitrogen, some bulbs have krypton or xenon for lower temps) not only because it makes them safer to handle and harder to break but mainly because it slows down the decay of the filament by slowing down its evaporation. It bounces tungsten atoms back on the filament.
ridaj 6y ago
LED lights and fluorescent lights are vulnerable too per the Wired article at https://www.wired.com/story/lamphone-light-bulb-vibration-spying/ https://www.wired.com/story/lamphone-light-bulb-vibration-sp... , just with different degrees of sensitivity
- DoofusOfDeath 6y ago
  That article seems to say that this technique works better with LED lamps vs. incandescent bulbs. I wonder if they're talking about direct line of sight to the LED chip. Most of the LED "bulbs" in my house use a frosted plastic housing around the LED chip, which I would guess to interfere with the sound recovery.
phkahler 6y ago
>> One thing that's not obvious to me from TFA is why an incandescent bulb is called out specifically. Because they produce light continuously. An led, CFL, or other will actually flicker at 120Hz. An incandescent bulb still has 120Hz power going in, but because it depends on heating to produce light and the filament has some thermal capacity, this is largely smoothed out.
- MisterTea 6y ago
  > An led, CFL, or other will actually flicker at 120Hz. In 60Hz countries. Also, if it has a constant current driver there will be PWM noise from the regulator.
- hoytech 6y ago
  I have noticed LED bulbs keep glowing for a short period of time after turning them off: https://www.quora.com/Why-do-LED-bulbs-keep-glowing-even-after-switching-it-off-and-then-they-slowly-dim-out https://www.quora.com/Why-do-LED-bulbs-keep-glowing-even-aft... I imagine there is still some flicker, but it seems to be smoothed out pretty well on LEDs also.
  - phkahler 6y ago
    I've seen that too. I think they're using a phosphor of some kind to convert UV wavelengths to visible light. That would have some persistence for those wavelengths.
- deleted 6y ago
  [deleted]
ponker 6y ago
Maybe it’s because an LED bulb is much heavier?

buran77 6y ago

Maybe the filament is more susceptible to vibration and "flickering". But it may just be my interpretation, the text doesn't really spell it out as such.

braythwayt 6y ago
A couple of other comments mentioned the filaments, but the article says nothing about clear bulbs. They are very much in fashion these days, but most incandescent bulbs are frosted, so it seems to me that if you want to use a laser on the filament, there would need to be some considerations around photons passing through the frosting and reflecting off the filament.
- buran77 6y ago
  The bulb doesn't have to be clear, the filament vibration would make the light flicker visibly (for sensitive equipment that is) even if the glass isn't clear. So it may be that the filament is far more susceptible to vibration than the glass on any type of light bulb. As I said, this is my interpretation, the text doesn't make it clear to me.
- steverb 6y ago
  I don't think it's about observing the filament directly, just that the filament basically being a spring is more susceptible to vibrations which would change the amount of light emitted. I am totally guessing at that, but it seems reasonable.
LgWoodenBadger 6y ago
The filament is in a vacuum...
- close04 6y ago
  Almost no incandescent light bulb has a vacuum inside. They are filled with low pressure inert gas (mostly argon sometimes mixed with nitrogen, some bulbs have krypton or xenon for lower temps) not only because it makes them safer to handle and harder to break but mainly because it slows down the decay of the filament by slowing down its evaporation. It bounces tungsten atoms back on the filament.

ridaj 6y ago

LED lights and fluorescent lights are vulnerable too per the Wired article at https://www.wired.com/story/lamphone-light-bulb-vibration-spying/ https://www.wired.com/story/lamphone-light-bulb-vibration-sp... , just with different degrees of sensitivity

DoofusOfDeath 6y ago
That article seems to say that this technique works better with LED lamps vs. incandescent bulbs. I wonder if they're talking about direct line of sight to the LED chip. Most of the LED "bulbs" in my house use a frosted plastic housing around the LED chip, which I would guess to interfere with the sound recovery.

phkahler 6y ago

>> One thing that's not obvious to me from TFA is why an incandescent bulb is called out specifically. Because they produce light continuously. An led, CFL, or other will actually flicker at 120Hz. An incandescent bulb still has 120Hz power going in, but because it depends on heating to produce light and the filament has some thermal capacity, this is largely smoothed out.

MisterTea 6y ago
> An led, CFL, or other will actually flicker at 120Hz. In 60Hz countries. Also, if it has a constant current driver there will be PWM noise from the regulator.
hoytech 6y ago
I have noticed LED bulbs keep glowing for a short period of time after turning them off: https://www.quora.com/Why-do-LED-bulbs-keep-glowing-even-after-switching-it-off-and-then-they-slowly-dim-out https://www.quora.com/Why-do-LED-bulbs-keep-glowing-even-aft... I imagine there is still some flicker, but it seems to be smoothed out pretty well on LEDs also.
- phkahler 6y ago
  I've seen that too. I think they're using a phosphor of some kind to convert UV wavelengths to visible light. That would have some persistence for those wavelengths.
deleted 6y ago
[deleted]

ponker 6y ago

Maybe it’s because an LED bulb is much heavier?