[PD] obscuring voices while maintaining intelligibility

[Jonathan Wilkes]

>________________________________
>From: katja <katjavetter at gmail.com>
>To: pd-list at iem.at
>Sent: Wednesday, September 21, 2011 5:29 PM
>Subject: Re: [PD] obscuring voices while maintaining intelligibility
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>On Wed, Sep 21, 2011 at 10:44 PM, Hans-Christoph Steiner <hans at at.or.at> wrote:
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>>I'm trying to come up with a simple voice scrambling technique that
>>leaves voices understandable, but makes them unrecognizable.  A key part
>>of this is to make it very hard to reverse the scrambling to make the
>>voice more recognizable.
>>
>>I'm currently thinking that a ring modulator would work well for this,
>>and it uses minimal CPU.  Can anyone think of a way to reverse the ring
>>modulation?  I attached my quick sketch.
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>That's a nice challenge. If I were CIA, I'd try to descramble like this: demodulate (division instead of multiplication) with a sine sweep while analyzing the spectrum. At the sweep frequency where the spectrum is a harmonic recipe: bingo, a human voice. Then you could demodulate that 0.1 second of sound with the found frequency. Not something to quickly do in a Pd patch though.
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>If your scrambler would modulate the modulation frequency continuously, with a noise signal, speech is still intelligible, but descrambling in the above described way would no longer be possible, as you can't find a harmonic recipe from a one sample fourier transform.
For the first [random] that you instantiate in a fresh Pd instance:

[bang(
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[random 20]
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[print Ladies_and_gentlemen--_the_random_number_14]


Similarly, the output from each instantiation of [noise~] will always be the same across 

platforms.

What about maybe using Linux's dev/random?


-Jonathan


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>Katja
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