Non-Contact Heart Sound Measurement Using Independent Component Analysis

A non-contact heart sound measurement method using independent component analysis (ICA) was successfully developed, and the measured heart sound was quantitatively evaluated with the signal-to-noise ratio (SNR). There have been recent developments in the automated diagnosis of cardiovascular diseases based on the measurement of heart sounds. However, measuring heart sounds require physical restraint. Here, we propose a non-invasive and non-constrained method for non-contact measurement of heart sounds using microphones. We successfully demonstrated this method by applying ICA to multi-channel measured sounds with a microphone array. Then, we quantitatively evaluated it by measuring "pseudo heart sounds" at a distance of up to 200 mm from the source using four microphones in an anechoic chamber and a conference room. SNR was improved by increasing the number of microphones. This method could measure pseudo heart sounds even in the presence of artificial noise created by heating, ventilation, and air conditioning systems and human voices. We suggested that measurable distance can be improved by using more microphones. Moreover, we successfully measured actual heart sounds at a distance of 160 mm from the chest wall. This non-contact heart sound measurement method provided valuable information about the heart, such as visual recognition of the first (S1) and the second (S2) heart sounds.