There were 15 minutes between the first air raid alert and the sounding of the all-clear signal.

从第一个空袭警报到警报解除号音其间有15分钟。

《柯林斯英汉双解大词典》

Fog sets in, call master at once. Began to keep on radar for detecting to the sea all round at an interval of every 20 minutes. Sounding by echo 52 fathoms. Standby Engine. Fog signal started.

雾起，立即召唤船长，开始保持每20分钟用雷达环扫一次海面，回声测深52拓，备车，开启雾号。

youdao

ICON USES an algorithm that digitally fuses together the best audio from its two electret microphones and its patented Voice Activity Sensor to create a single, natural sounding speech signal.

图标使用了一个算法，数字融合了来自两个驻极体麦克风和声音传感器专利的最佳音频创建一个单独的，自然的声音的语音信号。

youdao

Staff tell an apocryphal-sounding anecdote from the Search for Extraterrestrial Intelligence, when a promising signal turned out be a technician warming his lunch at the Arecibo Observatory in Puerto Rico.

BBC: Aye to the telescope