White Noise Generator

Discussion in 'General Discussion' started by HK_User, Jan 14, 2019.


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  1. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    Describe what is best to prevent recording your conversations and how to make or where to purchase.
     
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  2. deMolay

    deMolay Monkey+

    Prevent what from recording you?
     
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  3. sec_monkey

    sec_monkey SM Security Administrator

    ya need to place all cell phones in 2 to 4 freezer bags and put them in a refrigerator or freezer then disconnect and unplug all internet or cell connected devices in the room [ better yet the entire building ] .

    even that might not be enough.

    fer truly secure conversations ya need a SCIF
     
    Last edited: Jan 14, 2019
  4. deMolay

    deMolay Monkey+

    OK a tech illiterate here what is a scif? When he said white noise I thought he meant for tinnitus
     
  5. sec_monkey

    sec_monkey SM Security Administrator

  6. deMolay

    deMolay Monkey+

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  7. UncleMorgan

    UncleMorgan I eat vegetables. My friends are not vegetables.

    Cone of Silence.
     
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  8. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    I must ensure that any conversations between any two or more people must be secure. In that we are speaking of a face to face meeting within a simple concrete block building.

    This is not a speculative question but a matter of fact in what I do to aid Vets.

    Cell phones are not allowed>>>>.....
    But if all were honest I would not need to ask such a question as I have first hand information of a cell phone left on "Record" and retrieved later.
     
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  9. techsar

    techsar Monkey+++

    A white noise generator loud enough to prevent recording would also make it exceedingly difficult to carry on a conversation.

    Will a hand-carried metal detector pick up a cellphone or microrecorder?

    Short of a strip-search.....
     
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  10. sec_monkey

    sec_monkey SM Security Administrator

    ya have to worry about cell phones, recorders, computers or any other electronic device.

    ya would have to build a true Faraday cage, remove all electronics and search all occupants every time.
     
  11. deMolay

    deMolay Monkey+

    Sorry above my pay grade
     
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  12. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    We have limited access and no access to some. We are in the process of of installing thermal barriers that just happen to have foil on both sides of the foam panels.
    As always lack of funds and a Bldg that is not owned limits our efforts.
     
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  13. Salted Weapon

    Salted Weapon Monkey+++

    They used to have some great Audio Oscillators, that M.A.R.S, maybe even a surplus if they are still out there
    could make it hard to hear other frequencies like voices. There may even be more modern ones, but I likes the old ones that used
    tubes and potentiometeres, like the idea you are thinking about, but sometimes blending the sound is easier then eliminating it. But hey I am rusty at allot of this stuff.
     
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  14. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    "blending the sound is easier then eliminating it"
    That's the theory that is suggested but no test results. If you cover the hearing spectrum with something like this then you start to blend to a point where it becomes more difficult to record a conversation.
    The Ultimate White Noise Generator • Design Your Own Color
     
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  15. Salted Weapon

    Salted Weapon Monkey+++

    Oh so you want blocking but ability to record within the space?
     
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  16. Salted Weapon

    Salted Weapon Monkey+++

    I'm gonna pick my own brain.........love stuff like this...
     
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  17. sec_monkey

    sec_monkey SM Security Administrator

    unfortunately some bugs and recording devices might be immune to this and other countermeasures.

    russia n china have some sophisticated stuff n things n they have sold em to the wrong folks.
     
  18. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    I want anything recorded to be unintelligible in playback.
     
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  19. Airtime

    Airtime Monkey+++

    This is a simple question but it has a complex answer.

    To mask your voice, the noise (we’ll discuss color in a moment) needs to as loud or louder than your voice at the microphone of the listening/recording device. To be very intelligible to microphone or another person in the room, your voice needs to be better than 10 decibels louder than the noise at their ears. However, generally a speaking voice can still be mostly understood even if the noise is equal to the signal level and if the noise is 10 dB greater than the voice 60-70% of the speach can be discerned!

    upload_2019-1-15_1-44-14.

    So, if you and the noise source are the same volume and of similar frequencies, ignoring the reverberant field for the moment and considering only the direct sound field, you generally need to be well over 10 times the distance from the recoding device to be masked. Or, the noise needs to be a bunch lounder than you and you’ll need to be quite close to your friend to be heard. Considering rooms are reverberant and sound does bounce around, the distances between you and recording mic vs the noise source and the recording mic are generally less critical.

    An aside, the chart above has a percent intelligibility measurement. Many decades ago, the way this was measured was there was an official list of words and letters that a person would read. Listeners (I vaguely recall it was suppose to be 10 or more) would listen and copy down the words and then those were compared to what were read. If the listeners got 70% correct, that was 70% intelligibility. There are electronic methods now.

    Noise color. White noise has equal energy per frequency. Pink noise has equal energy per octave. As you go up in octaves, you double the number of frequencies in each octave, so white noise has a much brighter sound than pink noise. Put white noise through a -3 dB/octave low pass filter and you get pink noise. Pink is what is used to equalize sound systems. Brown noise is further filtered at -6 dB/octave.

    The problem is to properly mask a voice you need noise that has similar energies in the range of frequencies that human voice employs, which is roughly 125-8000 Hz.

    upload_2019-1-15_1-36-54.

    The higher frequencies are especially critical to be masked as they are what provide clear articulation. The higher frequencies above 500 Hz and generally in 2k to 4k Hz separate consonants like the letters C from P from T from B from E or separate A from K, etc. So white noise would be a reasonable choice but you don’t need that to extend beyond 8000 Hz or much below 125 Hz as there is no human voice energy to mask.

    Have fun
    AT
     
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  20. HK_User

    HK_User A Productive Monkey is a Happy Monkey

    Add to all this and I have combat damaged hearing so I have to depend on the electronics.
     
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