New York: The poor sound quality of the latest taped message attributed to al Qaida chief Osama bin Laden has created problems for American analysts in distinctly verifying his identity, senior Bush administration officials said.

Analysts at the US Central Intelligence Agency and National Security Agency were facing problems in analysing the tapes, the officials were quoted as saying.

The tape had been played over a telephone to the Arab satellite television station al-Jazeera on November 12, which would have wiped out the high and low frequencies that help distinguish voices, a media report said.

"But even if the quality had been superb, the government analysts would have faced pitfalls in trying to verify the voice," the 'New York Times' reported.

Identity of a person can be ascertained by analysing the voice, since the vocal tract physically differs from one person to another, but unlike verifying someone's identity through fingerprints, voice recognition is indirect.

The science of using computers and linguists to identify individuals by their speech has improved dramatically in the last several years, but still involves considerable guess work and speculation, according to experts.

The government's assessment so far that it cannot be absolutely certain that the audio tape broadcast on November 12 was recorded by Osama bin Laden does not surprise experts in the field of voice authentication, the paper said.

"If an impostor wanted to put together a tape, he could fool a lot of people," an expert was quoted as saying.

PTI