[Asterisk-Users] Realtime Voice Changer Patch

[trixter aka Bret McDanel]

On Thu, 2005-11-10 at 11:32 +1300, Matt Riddell wrote:
> Justin Tunney wrote:
> > I have just written a patch for Asterisk 1.2.0-rc1 that allows you to
> > install a voice changer on a channel.
> > 
> > http://www.lobstertech.com/voicechanger/
> > 
> > If you are a developer, please feel free to help add features and
> > clean up the patch so that we can hopefully get it in CVS some day.
> 
> YOU BASTARD!!!
> 
> :D
> 
> That was my secret "want to get it done someday" project!


I will give you one of my super secret someday projects.  A voice stress
analyzer built into asterisk (would be done in a similar way in terms of
interfacing, perhaps just play a beep or if non voice only circuit send
text).

VSAs work by detecting subharmonics present when a person is under
stress.  Basically when stressed there are slight increases in muscle
tension that pull on vocal cords this causes a specific set of
sunharmonics to shift upwards slightly.  Applying a dsp filter to that
and detecting those changes will result in a stress indicator. 

Most people are conditioned to believe lying is wrong (whether or not it
is I wont comment here).  As a result they exhibit stress when they lie.
This is how a polygraph works, by measuring physical responses to what a
subject thinks is wrong.

While this is not that accurate, you dont know what is causing the
stress, you can see when it presents itself in relation to what is
spoken and try to make some guesses.

The frequencies are generally between 8-14Hz.  While these frequencies
by themselves generally cannot pass a telephone network (300-3300Hz US
300-3400Hz EU typically) when mixed with other frequencies they can be
passed.  This is the same principle that china used for its C5 links
with america, a 2600+2400+60Hz tone followed by 2400Hz would seize the
line there (at least a few years ago, I dunno about now, or even if they
are still C5r1).  60Hz by itself cant go but it modifies the waveform of
the other tones and can be pulled out.

Now you have an all new super secret someday project so your list doesnt
get shorter ! :)

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
UK +44 870 340 4605   Germany +49 801 777 555 3402
US +1 360 207 0479 or +1 516 687 5200
FreeWorldDialup: 635378
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