Abstract: A method and apparatus for evaluating of implanted artificial (mechanical or bioprosthetic) heart valves includes a microprocessor responsive to a series of digital signals for processing a portion of the series of digital signals corresponding to valve sounds in a phonocardiogram. A deconvolution algorithm is provided to transform the portion of the series of digital signals into an impact history signal which characterizes the motion of the occluding elements and an impulse response signal. A microprocessor is used to transform the impulse response into a power spectrum signal and to calculate ring down times therefrom which characterize the physical structure of the valve cage. A recorder is provided for graphically portraying the extent and nature of degradation and deterioration of the heart valve. Such a printed graphic record of the impact history signal can then be precisely evaluated and a period-to-period comparison can be made with an earlier recorded impact history signal.

Abstract: Sound monitoring apparatus is described which provides a slowed down version of the original sound, e.g. a heart beat without changing the quality of the sound as perceived by a trained listener such as a physician. The amount by which the sound is slowed down can be varied by the user. The original sound is converted to an analog electrical signal, digitized and electronically processed in a microprocessor-based circuit such that digital data corresponding to cycles of the analog signal are stored in a random access memory. The microprocessor reads out the digital data a predetermined number of times corresponding to a number of sound cycles according to the rate set by the physician. The digital data is reconstituted into sound which is composed of replicated sets of cycles of the original sound. The repetition rate of the heart-beat in the output sound is a fraction of the repetition of the heart-beat in the original sound but the sound quality appears the same to the physician as the pitch is invariant.