Jeffrey O Townsend

US Patent:

6556967, Apr 29, 2003

Filed:

Mar 12, 1999

Appl. No.:

09/266811

Inventors:

Douglas J. Nelson - Columbia MD
David C. Smith - Columbia MD
Jeffrey L. Townsend - Columbia MD

Assignee:

The United States of America as represented by the National Security Agency - Washington DC

International Classification:

G10L 1520

US Classification:

704233, 704226, 704227, 704228, 704208, 704214

Abstract:

The present invention is a device for and method of detecting voice activity by receiving a signal; computing the absolute value of the signal; squaring the absolute value; low pass filtering the squared result; computing the mean of the filtered signal; subtracting the mean from the filtered result; padding the mean subtracted result with zeros to form a value that is a power of two if the result is not already a power of two; computing a DFFT of the power of two result; normalizing the DFFT result of the last step; computing a mean of the normalization; computing a variance of the normalization; computing a power ratio of the normalization; classifying the mean, variance and power ratio as speech or non-speech based on how this feature vector compares to similarly constructed feature vectors of known speech and non-speech. The voice activity detector includes an absolute value squarer; a low pass filter; a mean subtractor; a zero padder; a DFFT; a normalizer; and a classifier.