Apple has been granted a patent (number 9,218,809) for a “fast, language-independent method for user authentication by voice.” It involves a method and system for training a user authentication by voice signal.
In addition to standard password-type information, it’s now possible to include, in some advanced authentication systems, a variety of biometric data, such as voice characteristics, retina patterns, and fingerprints. In the context of voice processing, Apple says two areas of focus can be distinguished. Speaker identification is the process of determining which registered speaker provides a given utterance.
Speaker verification, on the other hand, is the process of accepting or rejecting the identity of a speaker based upon an utterance. Collectively, they refer to the automatic recognition of a speaker (i.e., speaker authentication) on the basis of individual information present in the speech wave form.
Most applications in which a voice sample is used as a key to confirm the identity of a speaker are classified as speaker verification. Many of the underlying algorithms, however, can be applied to both speaker identification and verification.
Here’s Apple’s summary of the invention: “In one embodiment, a set of feature vectors are decomposed into speaker-specific recognition units. The speaker-specific recognition units are used to compute distribution values to train the voice signal. In addition, spectral feature vectors are decomposed into speaker-specific characteristic units which are compared to the speaker-specific distribution values. If the speaker-specific characteristic units are within a threshold limit of the speaker-specific distribution values, the speech signal is authenticated.”