Effects of respiration on heart sounds using time-frequency analysis

The time-frequency (TF) diagrams of three recording sets at the aortic area are compared: normal breathing, held inspiration and held expiration. The TF analysis of heart sounds is proposed as an auxiliary method in cardiac auscultation. The continuous wavelet transform (CWT), using the Morlet wavelet, is applied to the cardiac cycles in order to observe the timing and frequency of the events. Time-frequency diagrams of sounds from pathological and non-pathological subjects are presented. Comparing the different manoeuvres provides extra information that may not be obvious in recordings during normal breathing, allowing a better identification of cardiac events