The peak time detecting circuit which is composed of full-wave rectification circuit and differential circuit can detect the reach time of echo signal accurately.

采用时间增益补偿技术，补偿超声波在空气中的衰减，减少回波信号的起伏；由有源全波整流电路和微分电路等组成峰值时间检测电路，可正确检测回波的峰值到达时间。

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He found that the length of time it takes a sound's echo to decay is determined by the absorption of the sound's original energy by surrounding material.

他发现，声音回声衰减的时间长短取决于周围物质对声音原始能量的吸收。

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The further off this solid obstruction, the longer time will elapse for the return of the echo.

固体障碍物越远，回声返回所用时间就越长。

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Black churchgoers, of course, often do the same thing at Sunday-morning services, and I suspect that the amenlike responses of black theatergoers are a not-so-distant echo of that old-time religion.

WSJ: Theatergoers: Can I Get an Amen? | Sightings by Terry Teachout

Across the uncertain ways of space and time our hearts echo those words.

WSJ: Thomas Fleming: An English Thanksgiving, 1942

On the other side, we see numerous examples of drug users and drug dealers on the streets or at some stage of the justice system, and time after time their economic backgrounds and family life echo a similar refrain.

FORBES: 'The House I Live In' - The Most Important Drug War Film You'll Ever See