US: In the same way as the anonymous author of "Primary Colours" was "outed" because of his use of language, US scientists have concluded with almost 100 per cent certainty that the tape played on al-Jazeera television on Tuesday came from Osama bin Laden, writes Conor O'Clery, North America Editor
They are not issuing a definitive finding, as old tapes can be spliced together to deceive a listener. Also the sound quality was poor as the tape was played over a telephone before reaching the television station. This distorted high and low frequencies that could help identify individual voices. A fake could be made by a male relative whose vocal tracts are similar.
But major advances in text and voice authentication have been made in recent years.
Examination of low level acoustics, such as phonemes lasting milliseconds, can build up a template around a person and provide over 90 per cent verification of a voice, said Mr Larry Heck, speech research director at Nuance Communications in California.
When one factored in the types of words people chose, how frequently they use them, how they pronounce certain words, along with melody and pitch, it was possible to get a higher percentage of certainty he said, speaking from his office in Silicon Valley, California.
One of the problems in verifying recordings is that reading from a script eliminates conversational speech patterns, Mr Heck said. In the al Jazeera tape as it is evident that the speaker is reading from a document as he recites such sentences as, "Why should fear, killing, destruction, displacement, orphaning and widowing continue to be our lot, while security, stability and happiness be your lot?" The "speech community" Mr Heck said, spent the last three decades developing statistical modelling techniques to identify voices and recently adopted other techniques from the "written community".
Dr Donald Foster of Vassar University in New York was able to establish that journalist Joe Klein wrote "Primary Colours" by examining linguistic patterns and word use in the text.
Government scientists fed the new tape and old authenticated recordings of bin Laden's voice into a computer with specially-designed software and they matched. Linguists at the National Security Agency which specialises in eavesdropping have concluded that the voice on the tape was bin Laden, US officials told the New York Times. Tests on the tape have also been done in Europe and the German interior ministry concluded it was genuine.