Modified adaptive noise canceller with an electrocardiogram to enhance heart sounds in the auscultation sounds

Purpose Heart sounds are basic factors to diagnosis cardiac diseases. To listen to heart sounds clearly, noises from auscultation sounds should be suppressed. Because a stethoscope provides just one channel, the general adaptive noise canceller is not appropriate to enhance heart sounds. Therefore, we proposed a modified adaptive noise canceller with an electrocardiogram to enhance heart sounds using a single stethoscope. Methods Auscultation sounds can be divided into heart sounds and non-heart sounds. The first heart beat (S1) appears when the R peak occurs on an electrocardiogram. After detecting S1, the second heart beat (S2) can be detected. Then, non-heart sounds are extracted by excluding S1 and S2 from the auscultation sounds. The proposed modified adaptive noise canceller uses the extracted non-heart sounds as reference input and suppresses auscultation sound noise. Results Two experiments were conducted to verify the performance of the proposed method. In the simulation, heart sounds were enhanced efficiently. In the experiment using clinical education database, heart sounds were enhanced about 7.7 dB. Conclusions Because auscultation sounds consist of various sounds occurring inside the body, heart sounds must be enhanced. We confirmed that the proposed method yielded good results. Therefore, it is expected that the proposed method can be applied to various cardiac diagnosis devices based on a computer system.