| 摘要 |
An electronic stethoscope having two listening heads, functionally equivalent to one another, each containing a microphone. The signal of one microphone is subtracted from the signal of the other microphone, and the resulting difference signal is amplified, using either analog or digital signal processing techniques. The amplified difference signal is transduced to sound by headphones. Sounds which originate in the plane equidistant from both microphones (the "midplane") are eliminated altogether, a fact which may be exploited to dissect a composite sound into two component sounds. Other sounds are attenuated in a predictable pattern, producing a focusing effect which increases as the microphones are brought closer together. The stethoscope incorporates features which minimize electromagnetic interference, enhance low-frequency throughput, reject amplified Johnson noise, and conserve battery power.
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