Speech-recognition software is used today by banks and other institutions to conduct customer transactions over the phone without the need for a live customer-service representative. But such systems recognize mainly numbers and words, not individual voices. If you utter the right PIN and account number, you get through.

Now a system being readied for commercialization in Europe treats an individual's voice as the gate-opener. That capability would add another security layer: while your PIN can be compromised, your voice is not so easily stolen. It could also eliminate the need to remember and recite account numbers and PINs.

Owned by Surrey, U.K.-based Biometric Security, the system, called Voice Vault, requires users simply to utter their name, birth date, and a password, says chief technology officer Vance Harris. The company, like others in the field, already has a handful of banks as clients, who use "voiceprinting" for internal security purposes. But Voice Vault's system will be made available to general account holders at an undisclosed European bank by December, says Harris.

The system will require a user to remember a minimal amount information, while relying instead on that person's voice for authentication. First, customers "register" their voices in a training session that involves saying words designed to capture the frequencies associated with their voice. The system then constructs a statistical model that predicts what a speech waveform would look like when the person is uttering an entirely novel sentence.

Then, when that person's account is accessed over a phone, the system not only confirms that the articulated name, birthdate, and password are accurate, but also checks to see if the waveforms of those utterances match the template stored with the account.

Such modelling of the vocal tract is a popular approach these days for voice verification, says Aladdin Ariyaeeinia, a voice researcher at the University of Hertfordshire, England. Indeed, many companies are developing similar systems.

Much farther in the future is so-called "text independent" identification, which would be so good at recognizing individual voices that you'd merely call your bank and say "What's my balance?" without having to give any other information.

Voiceprints have some over other biometrics too. Ariyaeeinia notes that while some banks are now looking at using more established forms of biometrics for online banking -- fingerprints and iris scans -- these require additional hardware to perform the scans.