[PD] obscuring voices while maintaining intelligibility

[Hans-Christoph Steiner]

On Sep 22, 2011, at 5:29 AM, Lorenzo Sutton wrote:

> On 21/09/2011 22:44, Hans-Christoph Steiner 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.
>
> Ineresting. Also these possible approaches come to mind:
>
> - Trivial, probably off-topic: use a TTS. Only thing that is  
> recognisable is the software which produced it.
> - Use some sort of granulation with random pitch-shifting. Not sure  
> how easily reversible this would be.
>
> A fun thing might be mix the two: that is start from a TTS and then  
> feed it into the granular... Here a silly example made with Festival  
> TTS and granulation in Granita (the first sentence is the 'original'  
> produced by Fesival) with different settings and degrees of  
> recognisability:
>
> http://lorenzosu.altervista.org/temp/dump/voice01.ogg



This paper has some good discussion on the technique:

http://www.efjohnsontechnologies.com/resources/dyn/files/75835/_fn/Selected_comments_on_scrambler_security.pdf

The hard thing to defeat would be statistical analysis techniques.   
Perhaps the idea is to try to modify to voice to sound as much as  
possible like a standard voice, like make them all have the same base  
pitch, then add a random warble.

.hc

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