Comparison of Envelope Detection and Signal Normalization Methods for Foetal Heart Rate Extraction from Foetal Heart Sound

Foetal heart rate is an important indicator of foetal well-being which indicates fetal distress during antepartum and intrapartum period. This paper provides systematic comparison of four different methods envelope detection and four different methods of signal normalization to determine the fetal heart rate from fetal heart sound. To obtain the ground truth, each heart beat was manually identified by visualizing the sound recording on a computer screen. Four different measure of error are used compare various combinations of envelop detection and normalization methods. It is found that the homomorphic filtering gave highest accuracy. Choice of normalization methods did not affect accuracy measurement in most cases.