An example of the subtraction filter for cleaning of respiratory sounds from the shock-type interferences at simultaneous two-channel recording

The systems for electronic auscultation of respiratory and cardiac sounds are vulnerable to accidental pulse (shock) interferences due to touching the sensors or friction of connecting cables. At multichannel sound recording, the most of such shocks are well-separable among the channels. This feature allows the constructing of simple technique for removing of shock-type interferences from the signals. The idea of proposed filter is based on estimation of weighted difference between the short-time frequency spectra of two signals synchronically recorded via the individual channels. Some typical examples approving the efficiency of such filtering are shown. The pros and contras of this approach are discussed.