Automatic Speaker Verification Using Cepstral Measurements

Automatic speaker verification was accomplished in this study using cepstral measurements to characterize short segments in each of the first two vowels of the standard test phrase “My code is .” The length of the word “my” and the speaker's pitch were used as additional parameters. The verification decision is treated as a two-class problem, the speaker being either the authorized speaker or an impostor. Reference data is used only for the authorized speaker. The decision is based on the test sample's distance to the nearest reference sample. Data is presented to show that, if reference samples are collected over a period of many days, then verification is possible more than two months later, whereas, if reference data is collected at one sitting, verification is highly inaccurate as little as 1 h later. Four authorized speakers and 30 impostors were examined, with error rates obtained from 6% to 13%. Impostors attempting to mimic the authorized speaker could not improve their ability to deceive the system significantly.