A New Digital Stethoscope with Environmental Noise Cancellation

A medical instrument for acquisition and analysis of phono-cardiac signals is described in the paper. The proposed system is based on an electronic stethoscope with enhanced performances in environmental noise reduction, achieved by means of two microphones whose signals are combined by an adaptive algorithm. A software tool able to reproduce, visualize and analyze cardiac sounds completes the system. The recorded data and the results of the analysis are stored in a database to build up clinical history of patients and to allow further consultations. A demonstrator of the tool has been realized. Experimental results show significant improvements in noise reduction, when the filtering algorithm is applied. These features make the instrument suited: i) to be employed in very noisy environment, such as ambulance, ii) to help physicians with acoustic diseases, increasing the sound level and showing the phonocardiogram, and iii) to retrieve basic information on the cardiac activity. Key-Words: Adaptive filters, System identification, Biomedical signal analysis, Electronic stethoscope, Analysis cardiac sounds.