Voice activity detector

A voice activity detector, comprising:

• a) an absolute value squarer, having an input for receiving a signal, and having an output;
• b) a low pass filter, having an input connected to the output of said absolute value squarer, and having an output;
• c) a threshold-crossing detector, having a user-definable threshold, having an input connected to the output of said low pass filter, having a first output, and having a second output;
• d) a mean subtractor, having an input connected to the first output of said zero crossing detector, and having an output;
• e) a zero padder, having an input connected to the output of said mean subtractor, and having an output;
• f) a Digital Fast Fourier Transformer, having an input connected to the output of said zero padder, and having an output;
• g) a normalizer, having an input connected to the output of said Digital Fast Fourier Transformer, and having an output;
• h) a classifier, having an input connected to the output of said normalizer, and having an output;
• and
• i) decision logic, having a first input connected to the second output of said zero crossing detector, having a second input connected to the output of said classifier, and having an output.

A method of detecting voice activity, comprising the steps of:

• a) receiving a signal;
• b) computing the absolute value of the signal;
• c) squaring the result of the last step;
• d) filtering the result of the last step to only pass low frequency components in the range of from 0-60 Hz;
• e) computing the mean of the last step;
• f) subtracting the mean computed in the last step from the result of step (d);
• g) padding the result of the last step with zeros to form the next highest power of two of the result of the last step if the result of the last step is not already a power of two;
• e) computing a Digital Fast Fourier Transform of the result of the last step;
• f) normalizing the result of the last step;
• g) computing a mean of the result of the last step;
• h) computing a variance of the result of step (f);
• i) computing a power ratio of the result of step (f);
• j) classifying the results of step (g), step (h), and step (i) as a type of known speech and known non-speech to which the results of step (g), step (h), and step (i) most closely compares, where the known speech and the known non-speech are each identified by a mean, a variance and a power ratio.