Digital Filters for Frequency Bands Selection of Auscultation Signals

For more reliable diagnostics of heart, lungs and other internal organs diseases may be helpful to use digital filters, in particular, for selection the Bell, Diaphragm and Extended mode frequency ranges from auscultation signal. The urgency of this task is caused by the fact that auscultation is currently one of the main methods of clinical investigations. At the same time, when using traditional acoustic phonendoscopes and stethoscopes, to obtain reliable diagnostic signals, as a rule, a highly qualified practitioner is required. The analog active and passive filters used in electronic stethoscopes cannot provide the required accuracy and reliability. In this work it is suggested to use digital filters for separation of diagnostically important ranges. FIR and IIR filters were compared and characteristics of IIR filters of different types with different characteristics were analyzed. On the basis of the analysis of real auscultation signals the recommendations on the choice of the IIR filter parameters for selection of the Bell, Diaphragm and Extended frequency ranges were elaborated. The results of the work can be applied in the construction of microcontroller stethoscopes.