pre-echo

例句：

1. 1. The echo of the bell was faint and distant.
   钟声的回声很微弱且遥远。
2. 2. The scientist used a special device to record pre-echoes from space.
   科学家使用一种特殊的设备来记录来自太空的预回声。
3. 3. The team worked diligently to improve their pre-echo detection system.
   团队努力工作，以改进他们的预回声检测系统。