Patent ID: 6519565
Filing Date: 2003-02-11
Classification: G10L

Abstract:
A method of comparing a challenge verbal utterance with several enrollment verbal utterances from the same individual to determine a security action, the method comprising the steps of:A) preparing an enrollment data comprising the steps of: a) creating a Fast Fourier transform of an electrical signal representation of a verbal enrollment utterance to produce an enrollment frequency domain representation thereof; b) taking M enrollment samples of the enrollment frequency domain representation for each of N frequency channels to form an M by N enrollment matrix E; c) determining if at least X of the M enrollment samples have a selected minimum energy content in at least Y of the N frequency channels; d) repeating steps (a) through (c) if the determination at step (c) is negative, and aborting after a selected number of negative repeats of steps (a) through (c); e) repeating steps (a) through (c) if the determination at step (c) is positive, until a selected number of said sample enrollment matrices Ei are formed as E1, E2, E3, . . . ; f) calculating the sums of the differences EDi between each Ei, as ED1=(E1âˆ’E2)+(E1âˆ’E3)+ . . . , ED2=(E2âˆ’E1)+(E2âˆ’E3)+ . . . ; g) comparing the enrollment samples pairwise by moving each sample forward and backward in time to obtain a best match; h) calculating an enrollment span, ES, equal to the difference between the largest and the smallest value of EDi; and i) accepting the enrollment data if: i. ES1, and ii. EDi2 exists, where R1 and R2 are selected enrollment criterion, B) challenging the enrollment data comprising the steps of: a) creating a Fast Fourier transform of an electrical signal representation of a verbal challenge utterance to produce a challenge frequency domain representation thereof; b) taking M challenge samples of the challenge frequency domain representation for each of N frequency channels to form an M by N challenge matrix C; c) determining if at least X of the M challenge samples have a selected minimum energy content in at least Y of the N frequency channels; d) repeating steps (a) through (c) if the determination at step (c) is negative, and aborting after a selected number of negative repeats of steps (a) through (c); e) calculating the sums of the difference CDi between C and each Ei, as CD1=(Câˆ’E1)+(Câˆ’E2), CD2=(Câˆ’E2)+(Câˆ’E3), CD3=(Câˆ’E3)+(Câˆ’E4), . . . ; f) comparing each one of the challenge samples pairwise by moving a the samples forward and backward in time to obtain a best match; g) calculating a challenge span, CS, equal to the difference between the largest and the smallest value of CDi; and h) accepting the challenge data only if: i. CS1, and ii. CDi2, exists, where V1 and V2 are selected verification criterion, C) enabling the security action if the challenge verbal utterance is accepted.