| US 7,577,564 B2 | ||
| Method and apparatus for detecting illicit activity by classifying whispered speech and normally phonated speech according to the relative energy content of formants and fricatives | ||
| Stanley J. Wenndt, Rome, N.Y. (US); and Edward J. Cupples, Rome, N.Y. (US) | ||
| Assigned to The United States of America as represented by the Secretary of the Air Force, Washington, D.C. (US) | ||
| Filed on Mar. 03, 2003, as Appl. No. 10/378,513. | ||
| Prior Publication US 2004/0176949 A1, Sep. 09, 2004 | ||
| Int. Cl. G10L 19/02 (2006.01) | ||
| U.S. Cl. 704—203 [704/214; 704/208] | 2 Claims |
| 1. Method for detecting illicit activity comprising:
classifying whispered and normally phonated speech by determining the relative amounts of fricative and formant energy in
each of two separate bandwidth samples of said speech wherein
said step of determining further comprising the steps of:
framing an input audio signal into 4.8 second data windows and advancing said windows at a rate of 2.4 seconds;
computing the magnitude of said data over a high frequency range from 2800 hertz to 3000 hertz;
computing the magnitude of said data over a low frequency range from 450 hertz to 650 hertz;
computing the ratio of the said magnitude from said high frequency range to the said magnitude from said low frequency range
by performing an N-point Discrete Fourier Transform; and
determining if said ratio is greater than 1.2;
IF said ratio is greater than 1.2, THEN
labeling said audio signal as whispered speech; and
categorizing the activity as illicit;
OTHERWISE,
labeling said audio signal as normally phonated speech; and
categorizing the activity as non-illicit.
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