>________________________________ >From: katja <[email protected]> >To: [email protected] >Sent: Wednesday, September 21, 2011 5:29 PM >Subject: Re: [PD] obscuring voices while maintaining intelligibility > > > > > >On Wed, Sep 21, 2011 at 10:44 PM, Hans-Christoph Steiner <[email protected]> wrote: > > >>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. > > >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. > > >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( | [random 20] | [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 > > >Katja >_______________________________________________ >[email protected] mailing list >UNSUBSCRIBE and account-management -> >http://lists.puredata.info/listinfo/pd-list > > > _______________________________________________ [email protected] mailing list UNSUBSCRIBE and account-management -> http://lists.puredata.info/listinfo/pd-list
