De-Noising of the Doppler Fetal Heart Rate Signal with Wavelet Threshold Filtering Based on Spatial Correlation

The fetal heart rate (FHR) signals provide valuable information for fetal development and well-being. However, the components of the original signals obtained by the Doppler ultrasonic method are very complex and seriously interfered by many factors, which makes it very difficult to extract heart rate. This present paper analyzes the characteristics of Doppler echo signals and applies the spatial correlation to estimate original noise variance, then develops an adaptive method calculating de- noising threshold, finally makes certain amendments for it in practice. The result of processing actual Doppler fetal heart sound signals proves that the method can effectively reduce the noise and extract fetal heart sounds, and calculate more accurately fetal heart rate by auto- correlation.