Morphological pure speech detection using valley percentage

A method for detecting pure speech signals in an audio signal having pure speech and non-speech or mixed-speech signals, the method comprising:

• filtering the audio signal to produce a clean audio signal, where the clean audio signal retains distinct boundaries between the pure-speech and non-speech portions, yet with less noise, wherein the filtering includes:
• converting the audio signal into an energy component having a plurality of energy levels, wherein each energy level corresponds to an audio sample of the audio signal;
• and
• applying a morphological closing filter to each energy level of the energy component to produce a filtered energy component of the audio signal by,
• positioning a first window over a plurality of energy levels such that a first energy level is positioned near a mid-point of the first window;
• dilating the first energy level to a maximum energy level of the surrounding energy levels viewed through the first window;
• repositioning the first window over a plurality of energy levels to a next consecutive energy level such that the next consecutive energy level is positioned near a mid-point of the first window;
• repeatedly performing the dilating and repositioning until all of the energy levels of the energy component have been dilated;
• repositioning the first window over the first energy level;
• eroding the first energy level to a minimum energy level of the surrounding energy levels viewed through the first window;
• repositioning the first window over a plurality of energy levels to the next consecutive energy level;
• and
• repeatedly performing the eroding and repositioning until all of the energy levels of the energy component have been eroded, resulting in a plurality of filtered energy levels of the energy component;
• computing from the audio signal a valley percentage feature;
• classifying the audio signal into either a pure-speech or non-speech classification according to the valley percentage feature;
• and
• determining the boundaries between a portion of the audio signal classified as pure-speech and a portion of the audio signal classified as non-speech.

A computer-readable medium on which is stored software for performing speech detection on an audio signal, the software, when executed by a computer, comprising instructions for:

• storing a plurality of predetermined parameters for detecting pure-speech signals in an audio signal having pure-speech and non-speech or mixed-speech signals;
• cleaning the audio signal to remove noise, wherein the audio signal comprises a plurality of audio samples in a first window, the first window having a size equal to one of the predetermined parameters;
• computing from the clean audio signal a valley percentage, wherein the valley percentage is computed from a plurality of audio samples in a second window, the second window having a size equal to another one of the predetermined parameters, and wherein the valley percentage represents for an audio sample the number of audio samples in the second window having an energy level falling below a threshold energy level as compared to the total number of audio samples in the second window;
• classifying the value of the valley percentage into either the pure-speech or non-speech classifications according to another one of the predetermined parameters;
• and
• determining the boundaries between a plurality of pure-speech and non-speech classifications by eliminating isolated pure-speech and non-speech classifications in a respective third and fourth windows, the third and fourth windows having sizes equal to another two of the predetermined parameters.

A computer-readable medium on which is stored software for performing speech detection on an audio signal, the software, when executed by a computer, comprising instructions for:

• storing a plurality of predetermined parameters for detecting pure-speech signals in an audio signal having pure-speech and non-speech or mixed-speech signals;
• cleaning the audio signal to remove noise, wherein the audio signal comprises a plurality of audio samples in a first window, the first window having a size equal to one of the predetermined parameters, the cleaning comprising:
• converting each audio sample in the first window into a corresponding energy level, the energy levels comprising an energy component;
• applying a closing filter to the energy component resulting in a corresponding clean audio signal, where the audio signal retains distinct boundaries between pure-speech and non-speech portions, yet with less noise;
• computing from the clean audio signal a valley percentage, wherein the valley percentage is computed from a plurality of audio samples in a second window, the second window having a size equal to another one of the predetermined parameters, wherein the computing comprises:
• determining a number of audio samples in the second window having an energy level falling below a threshold energy level, according to another one of the predetermined parameters;
• and
• setting the valley percentage equal to a percentage of the number of audio samples in the second window having an energy level falling below the threshold energy level, as compared to the total number of audio samples in the second window;
• classifying the value of the valley percentage into either the pure-speech or non-speech classifications according to another one of the predetermined parameters;
• and
• determining the boundaries between a plurality of pure-speech and non-speech classifications by eliminating isolated pure-speech and non-speech classifications in a respective third and fourth windows, the third and fourth windows having sizes equal to another two of the predetermined parameters.

A computer-readable medium on which is stored software for performing speech detection on an audio signal, the software, when executed by a computer, comprising instructions for:

• storing a plurality of predetermined parameters for detecting pure-speech signals in an audio signal having pure-speech and non-speech or mixed-speech signals;
• cleaning the audio signal to remove noises wherein the audio signal comprises a plurality of audio samples in a first window, the first window having a size equal to one of the predetermined parameters;
• computing from the clean audio signal a valley percentage, wherein the valley percentage is computed from a plurality of audio samples in a second window, the second window having a size equal to another one of the predetermined parameters;
• classifying the value of the valley percentage into either the pure-speech or non-speech classifications according to another one of the predetermined parameters, wherein the classifying comprises:
• comparing the value of the valley percentage to a threshold valley percentage, the threshold valley percentage having a value equal to another one of the predetermined parameters;
• and
• setting a value in a binary decision mask corresponding to the value of the valley percentage to a value of zero where the valley percentage is equal to or less than the threshold valley percentage, or to a value of one where the valley percentage is greater than the threshold valley percentage;
• and
• determining the boundaries between a plurality of pure-speech and non-speech classifications by eliminating isolated pure-speech and non-speech classifications in a respective third and fourth windows, the third and fourth windows having sizes equal to another two of the predetermined parameters.

A computer-readable medium on which is stored software for performing speech detection on an audio signal, the software, when executed by a computer, comprising instructions for:

• storing a plurality of predetermined parameters for detecting pure-speech signals in an audio signal having pure-speech and non-speech or mixed-speech signals;
• cleaning the audio signal to remove noise, wherein the audio signal comprises a plurality of audio samples in a first window, the first window having a size equal to one of the predetermined parameters, the cleaning comprising:
• converting each audio sample in the first window into a corresponding energy level, the energy levels comprising an energy component;
• applying a closing filter to the energy component resulting in a corresponding clean audio signal, where the audio signal retains distinct boundaries between pure-speech and non-speech portions, yet with less noise, wherein the applying includes:
• dilating the energy levels of the energy component in the first window;
• and
• eroding the dilated energy levels of the energy component in the first window;
• computing from the clean audio signal a valley percentage, wherein the valley percentage is computed from a plurality of audio samples in a second window, the second window having a size equal to another one of the predetermined parameters;
• classifying the value of the valley percentage into either the pure-speech or non-speech classifications according to another one of the predetermined parameters;
• and
• determining the boundaries between a plurality of pure-speech and non-speech classifications by eliminating isolated pure-speech and non-speech classifications in a respective third and fourth windows, the third and fourth windows having sizes equal to another two of the predetermined parameters.

A computer-readable medium on which is stored software for performing speech detection on an audio signal, the software, when executed by a computer, comprising instructions for:

• storing a plurality of predetermined parameters for detecting pure-speech signals in an audio signal having pure-speech and non-speech or mixed-speech signals;
• cleaning the audio signal to remove noise, wherein the audio signal comprises a plurality of audio samples in a first window, the first window having a size equal to one of the predetermined parameters;
• computing from the clean audio signal a valley percentage, wherein the valley percentage is computed from a plurality of audio samples in a second window, the second window having a size equal to another one of the predetermined parameters;
• classifying the value of the valley percentage into either the pure-speech or non-speech classifications according to another one of the predetermined parameters;
• and
• determining the boundaries between a plurality of pure-speech and non-speech classifications by eliminating isolated pure-speech and non-speech classifications in a respective third and fourth windows, the third and fourth windows having sizes equal to another two of the predetermined parameters, wherein the determining comprises:
• applying a morphological opening filter to the plurality of pure-speech and non-speech classifications in the third window;
• and
• applying a morphological closing filter to the plurality of pure-speech and non-speech classifications in the fourth window.

A method for extracting speech detection features in an audio signal having a mixture of speech and non-speech audio samples, the method comprising:

• determining an energy level for each of plural audio samples in an audio signal;
• extracting a speech detection feature for each of the plural audio samples by,
• determining a maximum energy level in a range of plural surrounding audio samples;
• calculating a threshold energy level as a fraction of the maximum energy level;
• and
• setting the speech detection feature based upon a percentage of the plural surrounding audio samples that have an energy level falling below the threshold energy level.

A computer readable medium on which is stored software for extracting speech detection features for an audio signal having a mixture of speech and non-speech audio portions, the software comprising instructions for:

• determining an energy level for each of plural audio samples in an audio signal;
• filtering the audio signal to clean the audio signal while preserving boundary distinctions in the audio signal;
• and
• extracting a speech detection feature for each of plural portions of the filtered audio signal, each portion including one or more audio samples, each speech detection feature based upon a percentage of surrounding portions of the filtered audio signal that have an energy level falling below a threshold energy level for the surrounding portions.

A method for extracting speech detection features for an audio signal having a mixture of speech and non-speech audio portions, the method comprising:

• determining an energy level for each of plural audio samples in an audio signal;
• extracting a speech detection feature for each of plural portions of the audio signal, each portion including one or more audio samples, each speech detection feature based upon a percentage of surrounding portions of the audio signal that have an energy level falling below a threshold energy level for the surrounding portions;
• setting a classification for each of the plural portions as speech or non-speech based upon a comparison of the extracted speech detection feature for the portion to a speech detection feature threshold;
• and
• filtering the classifications to remove isolated classifications, wherein an isolated classification has a value differing from a predominant value for surrounding classifications, and wherein the filtering uses one or more morphological filters.