Hi Roberto,

Thanks for sending the audio sample

Sounds like very simple "voice inversion" or "speech inversion"...wich is the most simple
scrambling system there is ...you can recover the original voice by mixing (actually distracting) it with a tone somewhere between
1000 and 4000 hz...there is a software program on my website called "voice scrambler/descramble 1.1" i think originally made by
(what a coincidence) an italian radio-amateur you can find in the "free software section of my website...

www.tetrascanner.com

You will have to experiment a little with your soundcard settings and levels to make it work

A hardware decoder can also be made using a: TBA120 chip (1 euro) or SO41P (1 euro)

You may also look in Germany where the same system is still in use by the German police i think a company called "VHT" have a
lowcost decoder for that. or you could check at the website of
CML microcircuits who have a scramble/descramble chip for speech inversion

Or just look on the internet using google for "speech inversion circuit" or "voice scrambler plans"

You may even be able to use a ssb receiver to decode it ...in that case you will have to transmit it first in am or ssb and then
receive it agian ...by "playing with the tuning dial" you could make it intelligible

Just remembered that you can decode it with 2 scanners that have a scramble decoder built-in

Yupiteru (do'nt remember wich model i think this one is not tunable)
Aor 8200 (have an option for a descramble module that can be tuned)

Greetings

Bla