VOA慢速英语:Scientists Use Sound Waves to Find Hidden Cracks in Bridges, Airplanes

短语讲解：

1. Thirteen people died and more than 140 others were injured.

more than 多于
例句：There is more than a whiff of propaganda. 
所含之宣传实在不止一点点。

2. Mr. Croxford says his ‘phased array' system of sending out sound waves returns harmonics -- echoes of different frequencies.

send out 发送;  发出
例句：I forget to send out your having believed. 
我忘记发你的信了。 

3. "By using this novel approach we can now pick up a crack close to a hole, which is directly relevant, to say, aerospace applications, where they're worried about cracks growing from rivet holes, things like that."

pick up 捡起; 接载
例句：I pick up my sister from her school. 
我到学校接妹妹。 
worry about 担忧
例句：Don't worry about being late. It's fine. 
别为迟到担心了 没有关系。