6 ms·

https://github.com/AsahiLinux/speakersafetyd https://github.com/AsahiLinux/speakersafetyd

CamperBob2 2y ago
Interesting. If the voltage across the speaker voice coil can be sampled with enough sensitivity at a fast-enough rate, you have an undocumented microphone.
- xyzzy_plugh 2y ago
  This is true of all speakers
  - CamperBob2 2y ago
    Exactly.
  - ssl-3 2y ago
    It's true of all dynamic speakers -- the sort with a voice coil and a magnet. (But not all speakers are dynamic speakers.)
    - planewave 2y ago
      Would this also be true for electrostatic speakers as well? Though would probably would require greater gain/amplification or, potentially the application of some kind of bias voltage for the capacitive diaphragm of the speaker. Just speculation based on the shared operating principal with condenser microphones
      - ssl-3 2y ago
        With bias power, I think an electrostatic loudspeaker turns into a condenser microphone (a thing that provides varying capacitance in response to changes in pressure). I don't think that electrostatic loudspeakers all require bias power, so it's not quite as simple as using a dynamic loudspeaker backwards is. It is a neat idea, though. A big, flat-panel microphone would be interesting to play with.
        robotresearcher 2y ago
        You can use a window or any large panel as a microphone without even touching it by observing its vibrations. You can bounce a laser off it, or even go fully passive using a camera with some sensitivity tricks: I recall a paper that reconstructed a remote conversation by watching a houseplant through a window.
        ssl-3 2y ago
        Of course. Everything is a microphone if you're brave enough.
  - BobbyTables2 2y ago
    But not true of all codecs… Do you think Apple put a hidden microphone in their devices by pure accident?
  - TacticalCoder 2y ago
    Others who know that better than me and commented but... First time I read that, as a kid, here was I plugging my headphones into the input jack of my parents' soundsystem and, sure enough, it worked as mic (although at as super ultra low volume but I clearly remember it worked).

Interesting. If the voltage across the speaker voice coil can be sampled with enough sensitivity at a fast-enough rate, you have an undocumented microphone.

xyzzy_plugh 2y ago
This is true of all speakers
- CamperBob2 2y ago
  Exactly.
- ssl-3 2y ago
  It's true of all dynamic speakers -- the sort with a voice coil and a magnet. (But not all speakers are dynamic speakers.)
  - planewave 2y ago
    Would this also be true for electrostatic speakers as well? Though would probably would require greater gain/amplification or, potentially the application of some kind of bias voltage for the capacitive diaphragm of the speaker. Just speculation based on the shared operating principal with condenser microphones
    - ssl-3 2y ago
      With bias power, I think an electrostatic loudspeaker turns into a condenser microphone (a thing that provides varying capacitance in response to changes in pressure). I don't think that electrostatic loudspeakers all require bias power, so it's not quite as simple as using a dynamic loudspeaker backwards is. It is a neat idea, though. A big, flat-panel microphone would be interesting to play with.
      - robotresearcher 2y ago
        You can use a window or any large panel as a microphone without even touching it by observing its vibrations. You can bounce a laser off it, or even go fully passive using a camera with some sensitivity tricks: I recall a paper that reconstructed a remote conversation by watching a houseplant through a window.
        ssl-3 2y ago
        Of course. Everything is a microphone if you're brave enough.
- BobbyTables2 2y ago
  But not true of all codecs… Do you think Apple put a hidden microphone in their devices by pure accident?
- TacticalCoder 2y ago
  Others who know that better than me and commented but... First time I read that, as a kid, here was I plugging my headphones into the input jack of my parents' soundsystem and, sure enough, it worked as mic (although at as super ultra low volume but I clearly remember it worked).