| 摘要 |
<p>The electronic stethoscope is designed to minimize the influence of the various types of noise while optimizing auscultation of the sounds of interest, and to enable a cardiologist to auscultate mechanical heart valves. It comprises a probe for sensing sounds of interest produced within a patient's body and for converting these sounds to an electric signal, and an audio amplifier and earphones for reproducing the sounds of interest in response to this electric signal. The stethoscope comprises: (a) a first filter unit having a frequency response that optimizes filtering of the tremor and passing of the low frequency sound components of interest in the range including the frequencies lower than 75 Hz; (b) a second filter unit having a frequency response that optimizes both attenuation of the ambient noise and passing of the sound components of interest in the range 110-1300 Hz, taking into consideration the variation of sensitivity of the human ear in function of frequency; (c) a third filter unit for passing the sounds of mechanical heart valves; and (d) a level detector detecting the amplitude level of the electric signal to activate a pulse generator of which the pulses are applied to the audio amplifier for momentarily and repeatedly disabling this audio amplifier when the detected amplitude level is higher than a predetermined amplitude level threshold.</p> |
