Tech Check: Tuning Key to Voice Systems

A big issue for businesses implementing voice authentication applications is how to tune the system to reduce errors known as false acceptances and false rejections. False acceptance occurs when an imposter gains access to a system; false rejection occurs when an authentic user doesn't. The frequency of these errors is measured using metrics known as false acceptance rates (FAR) and false rejection rates (FRR).

A voice authentication system plots the interplay of the two error rates against each other to establish an access threshold. If the threshold is changed to lower one error rate, the other one automatically goes up. To make a system effective, companies must strike a balance between the two, depending on the intent of their voice applications.

"With applications, it really does depend on the intent of speaker verification," says Kevin Farrell, director of speaker verification at ScanSoft. "If it's there as a customer-oriented convenience, and helps with costs in the call center, you might use a lower threshold, whereas you'd use a higher threshold for financial transactions."

But by themselves, FAR and FRR don't mean much, says Samir Nanavati, a partner at International Biometric Group. What matters, he says, is the combination of those with a third metric, the enrollment rate. "It doesn't matter what your FAR and FRR rates are if you fail to enroll 14% of your user population," he says.

What organizations should be looking at, says Nanavati, is a system's ability to verify. "From a business perspective, especially in the private sector, companies really don't care why you couldn't use a system. They primarily care that they have 12 million customers, and whether a system can handle that."


Copyright © 2003 IDG Communications, Inc.

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