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What a serious problem! The best solution that occurs to me might be  
replacing the voice, as in dubbing films into labguages. Is there  
budget to cover that?

Or possibly converting it to severe low rate MP3 and back to WAV,  
before the final encoding. I have not tried that so not sure. Or some  
kind of exotic voice processing such as Darth Vader?

<L>
Lou Judson  Intuitive Audio
415-883-2689


On Apr 15, 2010, at 2:24 AM, Ishumael Zinyengere wrote:

Using more complex effects, or combinations of effects, is also  
problematic, because, no matter how complex it gets, it is still  
possible to reverse engineer and make the voice recognizable.

We have considered the possibility of using compression to "destroy"  
the quality to such an extent that the voice of the witness could not  
be recognizable. The big problem with this is applying it  
selectively. We only want to distort the voice of the protected  
witness, not the voices of the lawyers, judges, interpreters etc.  
After all of the work that is going into producing redacted versions  
of the audio material, we don't want the end result to sound "bad".  
Also, using compression is obviously not an option with the redacted  
WAV files. (Identifying the portions of the recordings in which a  
protected witness's voice can be heard is a part of the redaction  
process.)


One idea that has been suggested is severely limiting the frequency  
bandwidth. This is similar to the idea of using compression: making  
bad quality work for us by "throwing away" information so it cannot  
be retrieved. Sort of an extreme version of a telephone voice. This  
seems like it could address most of the issues we've identified: it  
can be applied selectively and it shouldn't be too disturbing to the  
listener. We are doing some experiments with this option, but would  
be very curious to hear if anyone has any experience using this type  
of vocal distortion. Does it sound like it might work? Any other  
suggestions?

Any assistance would be greatly appreciated