Noise detection during heart sound recording.

Heart sound is a valuable biosignal for early detection of a large set of cardiac diseases. Ambient and physiological noise interference is one of the most usual and high probable incidents during heart sound acquisition. It may change the prominent and crucial characteristics of heart sound which may possess important information for heart disease diagnosis. In this paper, we propose a new method to detect ambient and internal body noises in heart sounds. The algorithm utilizes physiologically inspired periodicity/semi-periodicity criteria. A small segment of clean heart sound exhibiting periodicity in the time and in the frequency domain is first detected. The sound segment is used as a template to detect uncontaminated heart sounds during recording. The technique has been tested on the heart sounds contaminated with several types of noises, recorded from 68 different subjects. Average sensitivity of 95.13% and specificity of 98.65% for non-cardiac sound detection were achieved.