Detecting the split within heart sounds using a switched-capacitor filter

When making heart sound recordings, it is important to identify key features in real time, i.e. just prior and during the recording process. Hardware filtering on the incoming signal provides a means of getting a clearer picture. Using a switched-capacitor band-pass filter tuned to the characteristic domain frequency of the first heart sound, SI, enables observation of the split of SI into the Mitral and Tricuspic components M1 and T1. This contribution discusses results from setting up a practical system and what limitations were encountered.