他们听见了一种像是巨大爆炸的声音。

They heard what sounded like a huge explosion.

《柯林斯英汉双解大词典》

不久他们听见了枪声。

Soon they heard the sound of guns.

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他们听见了说话声。

They heard voices.

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And, at the very beginning there was a train that went around the Wall of Paris, more about the walls of Paris another time, that's fun to talk about, and Parisians would take picnic lunches, and they'd get on the train, and then they'd hear these large explosions and realize that they could get killed by these large explosions.

一开始的时候,有一趟火车,是绕着巴黎城墙行驶的,下次我们多讲讲巴黎的城墙,这挺值得一谈,巴黎人会带着午餐便当,坐上火车,然后他们听见了巨大的爆炸声,突然意识到他们可能会被炸死

耶鲁公开课 - 1871年后的法国课程节选