1. Even the boom that happens when the jet breaks the sound barrier went unnoticed.
    也察觉不到飞机冲破声障时发出的隆隆声。

2. The subtlety of his remarks was unnoticed by most of his audience.
    大多数听众都没有觉察到他讲话的微妙之处。

3. The Ombudsman´s prompt action at once put an end to an unpleasant practice which might have gone unnoticed.
    司法特派员及时采取的行动，迅速制止了这一起不愉快的事件，不然这件事可能因未得到人们注意而不了了之。

4. She hoped to remain unnoticed, but her white gown revealed her to him.
    她不想让他看见自己，但她的白色长袍泄露了踪迹。

5. If they had only had one more child, the fact would have passed unnoticed.
    如果他们只添了1个孩子，这件事本来就不会引起任何人的注意。