Determining a heart rate and a heart rate variability

A system (102) for determining a heart rate and a heart rate variability of an individual, the system (102) comprising:

• a memory (206);
• and
• a processor (202) coupled to the memory (206), wherein the processor (202) executes program instructions stored in the memory (206), to:
• capture heart sound of an individual;
• amplify an audio signal of the heart sound;
• detect an envelope of the amplified audio signal, wherein the envelope of the amplified audio signal is detected by:
• squaring of the amplified audio signal to obtain emphasized high amplitude components and diminished low amplitude components of the audio signal;
• applying a filter on the audio signal upon squaring, wherein the filter is configured with a pass band of 0.7 to 3.6 Hz;
• and
• applying a Teager-Kaiser Energy Operator (TKEO) on the audio signal filtered to obtain the envelope of the audio signal;
• detect peaks in the envelope of the audio signal, wherein the peaks are detected by;
• calculating difference in magnitude of a current point in the audio signal with an average of magnitude of earlier points in the audio signal from last detected peak or initial sample value in the processing window of the audio signal when no peak is detected;
• and
• evaluating if (a) the difference is positive and (b) a next subsequent data point is equal to or lesser than the current point, in order to culminate in actually detecting that the current point is a peak;
• classify peak to peak distance in the envelope into at least two clusters, to identify and correct false negative peaks and false positive peaks in the envelope of the audio signal;
• wherein the cluster comprising a higher peak to peak distance includes false negative peaks;
• and the cluster comprising a smaller peak to peak distance corresponds to detection of false positive peaks;
• correct the false positive peaks by:
• calculating a mean and a standard deviation of all the peak to peak distances that are present in the cluster having smaller peak to peak distance;
• inspecting every peak from a common peak, that has an adjoining correct peak to peak distance;
• identifying if a next detected peak has a peak to peak distance less than the difference of the mean and the standard deviation;
• and
• discarding the next detected peak;
• and
• determine a heart rate and a heart rate variability for the individual using the peaks detected.

A computer program product comprising a non-transitory computer readable medium having a computer readable program embodied therein, wherein the computer readable program, when executed on a computing device, causes the computing device to:

• capture heart sound of an individual;
• amplify an audio signal of the heart sound;
• detect an envelope of the amplified audio signal, wherein the envelope of the amplified audio signal is detected by:
• squaring of the amplified audio signal to obtain emphasized high amplitude components and diminished low amplitude components of the audio signal;
• applying a filter on the audio signal upon squaring, wherein the filter is configured with a pass band of 0.7 to 3.6 Hz;
• and
• applying a Teager-Kaiser Energy Operator (TKEO) on the audio signal filtered to obtain the envelope of the audio signal;
• detect peaks in the envelope of the audio signal, wherein the peaks are detected by;
• calculating difference in magnitude of a current point in the audio signal with an average of magnitude of earlier points in the audio signal from last detected peak or initial sample value in the processing window of the audio signal when no peak is detected;
• and
• evaluating if (a) the difference is positive and (b) a next subsequent data point is equal to or lesser than the current point, in order to culminate in actually detecting that the current point is a peak;
• classify peak to peak distance in the envelope into at least two clusters, to identify and correct false negative peaks and false positive peaks in the envelope of the audio signal;
• wherein the cluster comprising a higher peak to peak distance includes false negative peaks;
• and the cluster comprising a smaller peak to peak distance corresponds to detection of false positive peaks;
• correct the false positive peaks by:
• calculating a mean and a standard deviation of all the peak to peak distances that are present in the cluster having smaller peak to peak distance;
• inspecting every peak from a common peak, that has an adjoining correct peak to peak distance;
• identifying if a next detected peak has a peak to peak distance less than the difference of the mean and the standard deviation;
• and
• discarding the next detected peak;
• and
• determine a heart rate and a heart rate variability for the individual using the peaks detected.