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Lung sound cancellation method and apparatus

  • US 4,672,977 A
  • Filed: 06/10/1986
  • Issued: 06/16/1987
  • Est. Priority Date: 06/10/1986
  • Status: Expired due to Fees
First Claim
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1. A method for deriving low and high frequency heart sounds comprising the steps of:

  • a. detecting first and second acoustic signals from the thorax of a patient, said first acoustic signal being obtained from the cardiac region and said second acoustic signal being obtained from an axillary region;

    b. converting said first and said second acoustic signals to respective first and second output electrical signals;

    c. automatically amplifying said second output electrical signal by a predetermined factor;

    d. subtracting said amplified signal from said first output signal to thereby obtain a heart sound signal free of lung sounds;

    e. detecting a phase difference in said output electrical signals by transmitting sound waves of predetermined frequencies into the patient, receiving said transmitted sound waves at the cardiac region and the axillary region, and producing electrical signals in response thereto; and

    f. compensating for said phase difference by delaying said output electrical signal from the region which first produces an electrical signal in response to said transmitted sound waves to correspond with said output electrical signal from the second region.

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